NO744080L - - Google Patents

Description

Method and device for automatic

reading and determination of reaction results

taters

The present invention relates to a method and device for automatically reading and determining results from many virological, bacteriological and hematological reactions.

The device can also be used in the same way as a spectrophotometer, e.g. for the measurement and determination of chemical far-reaction results.

When testing in laboratories to find disease-causing substances, or when determining the content of various substances in the body, investigations of numerous reactions must often be carried out. During these investigations, one will have to handle hundreds and even thousands of test tubes containing, for example, dilution series or chemical color reactions.

Within virology, one can confirm a disease or obtain a diagnosis by isolating the virus itself or parts of it and visualizing these in an electron microscope. In addition, a diagnosis is often obtained by detecting an increase in the antibody titer in the blood for the respective virus or by detecting virus antigens in the cells.

In order to use the basic methods of virology to clarify which disease-causing substances occur in the patient's samples, dilution or titration of samples takes an important place in many methods. The research methods often use reactions whose results can be read visually from the dilution series. Such reactions include hemagglutination, binding of complement and inhibition of heiu-.-;-agglutination.

It is often the case that each sample must be diluted several times in succession, and control titrations must also often be carried out to increase the reliability of the test results. Thereby processed to and. with thousands of testers, and the results are read visually. The result is determined with current methods mainly by hand. Such a reading and determination of results is naturally slow,

and the possibilities for error are many. ,

In bacteriology, one seeks to obtain a diagnosis in many respects in the same way as in virology.

In a majority, bacteriological research methods are used

dilution series, and the results are read visually. More common methods of this type include the hemolysis reaction-based determination of the antistreptolysin titer (AST) for streptococcal bacteria, and the titration of staphylococcal bacteria (ASTA). With the Widal test, a reaction based on bacterial agglutination is used to determine which salmonella or typhoid type the sample may contain.

In haematology, in connection with water group determinations, one often has to deal with large quantities of samples, especially when there are many samples, whereby the results are read visually.

Numerous measurements with spectrophotometers are carried out daily in the laboratories. In few commercial devices of this type, automation occurs, as the measurements and result determinations are done manually. In some devices, one can automatically measure and determine the results of, for example, 1 lOO samples. In these available spectrophotometers, the light is guided perpendicularly through the walls of the cuvette, whereby the light cannot hit e.g. precipitates on the bottom of the cuvette.

In the device according to the invention, the light is directed in the direction of the cuvette's longitudinal axis through the liquid soil and the adjacent cuvette bottom or in the opposite direction. If the liquid volume in the cuvette is changed, the distance the light passes through in the liquid is also changed, whereby the permeability or transmittance of the liquid soil also changes. When the light travels in the cuvette's longitudinal direction, the precipitates, cloudiness etc. caused by serological, bacteriological or haematological reactions can be measured on the bottom of the cuvette on the basis of a change of a certain order of magnitude in the intensity of the light. Such precipitation or clouding on the bottom of the cuvette cannot be measured with available spectrophotometers. In e.g. hemolysis reactions, the hemolysis causes a clarification of the entire reaction mixture, which in turn increases the penetration of light into the liquid. Even here, a certain degree of hemolysis or reaction result can be determined by a given change in light intensity.

The method according to the invention is characterized by the fact that in the cuvette, row of cuvettes or group of cuvettes present in place at the time of the measurement, the liquid column calculated for reading and measurement and the adjacent cuvette bottom is led through the place in each cuvette (C, 10) the light (2, 8) in the reading device to go in the direction of the longitudinal axis in each cuvette (C, 10) from the light source on one side of the cuvette (C, 10) to the detector (3, 14) on the other side of the cuvette, whereby, when the light reaches runs in the direction of the cuvette's longitudinal axis, results from ^serological, bacteriological or haematological reactions or color reactions can be read on precipitates, flaking, etc. on the bottom of the cuvette or cuvettes present in their place, or in the liquid soil, ora they have not sunk to the bottom, and which have caused change, or on a color change in the liquid in the cuvette or cuvettes which produces a change in the permeability to light, on the basis of a certain .dependency ig change in the intensity of the light.

The device according to the invention is characterized by the fact that it includes groups of cuvettes that can be placed in a cuvette stand, whereby the relative position of the stationary or removable cuvettes is the same as that of the detectors and corresponding light sources in the measuring device, and that the measuring window of the cuvettes is suitably surrounded on the outside by a cylindrical protective part or edge.

In some commercially available cuvettes where the measurement is carried out horizontally through the cuvette walls, which can easily be scratched and soiled by touching with the fingers, even large errors in the measurements can be obtained. Furthermore, in the current devices where the light travels horizontally, insufficient attention has been paid to the arrangement of the cuvettes, and often this has not been taken into account at all.

In the laboratories, the preparation of reaction mixtures and their measurement in photometers form the daily work routine. In the reaction mixture, which is obtained by transferring a sample and one or more reagents to the cuvette with a pipette, the content of a certain substance or its enzyme kinetics is measured in photometers. In such measurements, errors can occur in the final result, depending either on errors in the devices used or on errors in the operation. Ernest Maclin and colleagues (Clinical Chemistry 19/8, 832 - 837, 1973) have demonstrated that the end result of the enzyme kinetics measurement can be - 40% incorrect at most. This error has been due to the equipment, inaccuracies with regard to the length of the light path in the cuvette, the temperature, the transfer of the sample and reagents with the pipette, the time as well as the photometer's optics and electronics.

Current developments favor the use of as little as possible sample and reagent quantities when preparing reaction mixtures. So-called micro methods have been adopted. This saves reagent consumption, and several determinations can be carried out on one sample, which can sometimes be very difficult to obtain.

When adapting micro methods, the volumes that need to be transferred with a pipette are very small, which is why the percentage error can also be significant and give an incorrect final result. Likewise, the error in the final measurement result increases with photometric measurements where the reaction mixtures are manufactured using micro methods.

The invention is illustrated in more detail in the following description and the accompanying drawings in which: Fig. 1 and 2 show schematically examples of different embodiments of the new reading device, Fig. 3a and 3b show two examples of result cards used in the result determination part, and in which it is possible by means of the reading device to record results by the name of each individual patient, Fig. 4 shows a group of cuvettes placed in the cuvette stand in measurement position seen from the side, Fig. 5 shows, seen from above, a group of cuvettes placed in the cuvette stand,

Fig. 6 shows one cuvette group seen from the side,

Fig. 7 shows the cuvette group's lid disc seen from the side,

Fig."8 shows the cuvette group seen from above,

Fig. 9 shows a section of a single cuvette seen from the side, Fig. 10 shows the cuvette group and its associated cuvettes

device for measurement,

Fig.11 shows a reagent block seen from the side,

Fig.12 shows a section of a cuvette group together with spis- tendon of a multistage serial pipette seen from the side, Fig.13 shows the pipette group and the tips of the serial pipette in

fig. 2 when the serial pipette's liquid container is filled,

Fig.14 shows a reagent block seen from above, and

Fig. 15 shows, seen from the side, a section of the cuvette group equipped with the lid according to the invention and placed in the photometer for measurement.

Titrations and other reactions are carried out in cells which are arranged symmetrically in the rack in several rows with a certain space between them. Such a cuvette stand is suitably constructed for the reading device. In that in fig. 1 shown preferred example is there on

the holder 1 placed light sources 2 (LI, L2, L3) and detectors ,3 (Dl,

D2, D3) with the same mutual distance as the cuvettes C. The light sources 2

and the detectors 3 can be connected to the reading device .f. e.g. in the same number as the cuvette lines. In this case, the holder 1 at the cuvette lines is arranged to be automatically movable from one cuvette to the next, or the cuvette rack can move<*>, and the holder is stationary. The device can of course also be constructed so that for each cuvette there is a light source and a detector corresponding to the light source, since the device lacks mechanically movable components.

When the light e.g. goes from the light source Li and through the cuvette

Cl in the direction of its longitudinal axis, the light first hits the liquid surface and then passes through the liquid soil over the bottom of the cuvette to the detector Dl corresponding to the cuvette Cl. The measuring device 4 thereby registers a light intensity of a certain magnitude. In this way, the reading device measures each cuvette in the cuvette row. A characteristic light intensity variation of a certain magnitude for some of the cuvettes in the row depending on precipitation,

turbidity on the bottom of the cuvette or on the permeability of the liquid present in the cuvette to light, provides information e.g. about the sought-after change point in the dilution series, and from the result determination it can be read which the respective cuvette in the series was.

In part 5 for determining the result, either a fixed logic circuit or a computer can be used for receiving results, storing and programming them, as the result is obtained in broken form. For each titration, the size of its specific light intensity, i.e. the result point, is determined experimentally. To determine the result, you can use those on fig. 3a showed a result card with the reaction's name 6 and the reaction's corresponding code 7

for its light intensity variation. Another possibility is that the part for determining the result has regulators that are set in positions corresponding to each reaction's characteristic light intensity difference and standard, after which the part for determining the result writes the reaction's name and result on the result card as shown in fig. 3b.

The reading device can be used as a spectrophotometer if the measuring device registers the amount of light coming from the light source to the corresponding detector, and the result part reports the degree of absorption and/or the degree of transmission for the solution in each cuvette.

Fig. 2 schematically shows another adapted example of a reading device with a common light source 8, the light being guided by means of fiber optics 9 through the cuvette 10 to fiber optics 11. Then the propagation of the light continues in the fiber optics to a circular periphery. The fibers communicating with the circle periphery read the reading end 12 one after the other, and the fiber optic 13 guides the light to the detectors 14.

The plant according to the invention mainly includes a cuvette unit. In the holding plate 17 of the cuvette group 16, there are several cuvettes 18 at a certain distance from each other. In these cuvettes, the degree of liquid absorption present in the cuvette 18, the light intensity change caused by the precipitation or turbidity on the bottom of the cuvette, is measured according to the vertical measurement principle. The vertical measurement principle means that the light passes over the bottom of the cuvette 18, and the light intensity is recorded using the detector 19 above the cuvette.

Each cuvette 18 in the cuvette group 16 can. is closed at the same time as the lid plate 20 during the time the cuvette group 16 is stored or shaken. The cuvettes 18 of the cuvette group 16 are arranged in such a way that the vertical measurement principle can be carried out.

The measuring opening 2 in the cuvette group 16 cuvettes 18 is surrounded on the outside by a cylindrical part or edge 22 which protects the measuring opening 2 against soiling and scratches, in order to maintain the optical standard of the measuring opening 2 in the cuvette groups 16 cuvettes 18.

If the bottom of the cuvette is concave on the inside, the precipitate in the cuvette forms a regular "knob" in the middle of the bottom of the cuvette. When the bottom of the cuvette is concave on the inside and flat on the outside, the propagation of light is only affected by a plano-concave lens. Then it is easy to produce cuvettes with identical optical properties. When the system is used as a spectrophotometer, the bottom of the cuvette can also be flat, as the propagation of light is not affected by a lens.

When the base 21 in the cuvettes 18 of the cuvette group 16 is flat, the bottom of the cuvette is easy to manufacture, and no optical errors occur there, nor any lens effect on the path of light.

However, depending on the purpose, the base and/or lid of the cuvette group's cuvettes can be flat, concave or convex to produce an appropriate inward or outward effective lens effect.

The lower part of the cuvette group 16 cuvettes 18 is preferably conical, so that the cuvettes of the cuvette group are easy to align (see fig. 10), as the particles from the liquid layer at the upper part of the cuvettes form a suitable button-like deposit on the bottom of the cone 23. Thereby it is easy within a small area to measure pollution and precipitation.

On the vertical inner wall of the cuvette 18, there may be one or more screens 24 in the direction of the longitudinal axis of the cuvette which convey

the mixture of the liquid in the cuvette 4 by shaking. When shaking with an external mixing device, the liquid soils in round cuvettes are brought into rotating motion, as the liquid soils rise along the walls of the cuvette. This means that the different liquid layers do not mix well. If there however

on the wall there are screens 24 as described above, these screens 24 cause eddies in rotating liquid columns, as the different liquid layers are effectively mixed even with little force.

It is also important that the cuvette group 16 can only be placed in one position in the cuvette stand 15. The cuvette stand 15 has a projection 25 which fits into a recess 26 or opening in the cuvette unit 16 holding disc 17. In the cuvette unit 16 holding disc 17 there is also a code 27, with which the respective cuvette group 16 in the measuring device and/or can be visually identified at the same time as each sample in the cuvette group 16 cuvette 18. The advantage of this is, among other things, that nine different samples can be identified with only one single code 27, and coding of each sample is avoided.

As the cuvette groups 16 can only be placed in one position in the cuvette stand 15, where the measurement of the cuvette groups 16 cuvettes 18 is carried out, in this case the nine channels of the measuring device can be set to zero with the first cuvette group 16, and with the following cuvette groups measure the respective cuvettes with the respective channels . The advantage of this is that if small optical errors occur during the production of the measuring openings 21 for the cuvette groups 16, and the error is repeated for each cuvette group, these are eliminated in the zero setting operation and in subsequent measurement operations.

The cuvette stand 15 is arranged in such a way that one or more cuvette groups 17 can be placed in it, and the stand can then be pushed through the measurement head of the measuring device (see fig. 4).

The cuvette stand 15 functions as a holder for the cuvette groups 16, e.g. during their storage, transport, when dosing liquid to and from these, as well as during the reaction's incubation and measurements.

The cuvette stand 15 can also be thermostatically controlled, as the appropriate temperature is achieved in the cuvettes 18 of the cuvette groups 16 and the liquids in them.

When the cuvette group 16 is in measuring position in the cuvette stand 15 at the measuring end of the measuring device, each cuvette in the cuvette group is protected from outside light, and the cuvette stand also provides protection from light to the cuvettes of the cuvette group between themselves.

When the cuvette group 16 present at the measuring end of the measuring device in the cuvette stand 15 arrives at the measurement location, the light beam can pass via an opening 28 in the cuvette stand 15. Between 29, 29', this light beam gives an impulse to the setting part 30 of the measuring end through the mediation of the detector 29' or a LED.

This setting part 30 aligns each cuvette 18 in the cuvette group 16 simultaneously on the light fibers and detectors corresponding to the cuvettes 18. When the hinge part 30 is moved to its upper position, the conical lower part 23 of each cuvette 18 in the cuvette group 16 has been placed in the conical part of the setting part, and furthermore the cuvette group 16 is at the measuring end, whereby the upper part of the cuvette group 16 rests against the detector head body at the measuring end. The measurement takes place in this position. In this way, the cuvette group 16 cuvettes 18 are arranged in an extremely close way. After a certain time, the measuring end's setting part 30 is lowered and allows the cuvette group 16 to sink back to its rest position in the cuvette stand 15, whereby the cuvette stand can be pushed forward in the measuring end either mechanically or manually. When the following cuvette group 16 arrives at the measuring point, the setting part 30 of the measuring end aligns and locks the following cuvette group in the measuring position.

The reagent block 33 (fig. 11) and the cuvette group 16 (fig. 12 and 33) are of a uKk model, e.g. devices comprehensive. 9 test tubes or cuvettes from or to which 9 different samples can be simultaneously transferred using a multi-stage serial pipette with 9 channels. In the reagent block 33 and in the cuvette groups 32, a certain number of finished doses of the same or different reagents can therefore be stored.

With the help of the lid of the reagent block 33 and the cuvette group 32, each tube 33a in the reagent block 33 or each cuvette 32a in the cuvette group 32 can be connected at the same time. With this lid 31, it is thus possible to prevent the liquids from drying out and the substances present in the tubes 33a or in the cuvettes 32a being contaminated. In addition, with the cuvette group lid 31, each cuvette 32a in the cuvette group 32 can be connected so that the bottom plane 31b of each plug 31a in the lid 31 is pressed under the liquid surface 34 in the cuvette 32a in the cuvette group 32 which corresponds to the plug 31a and at the point via which the light from the liquid continues to the detector 40. The lid 31 of the cuvette group 32 forms a continuous disc whose holes continue downwards in the form of downwardly directed plugs 31a, whose continuous cavity at the lower end is closed by means of a transparent bottom plane 31b. The stoppers 31a in the lid 31 of the cuvette group 32 are designed in such a way that when the lid 31 is in place in the cuvette group 32, a free air space is formed between the vertical or oblique outer wall of the stoppers 31a of the lid 31 and the inner walls in the upper parts of the cuvette group 32 corresponding cuvettes 32a.

When measuring the absorption in the liquid in the cuvette 32a of the cuvette group 32 with a photometer that works according to the present vertical measurement principle, the length of the light path h in the liquid in the cuvette 32a is equal to the path between the bottom plane 36 of the cuvette 32a and the bottom plane 31b on the stopper 31a of the lid 31. This way h can be regulated by producing

cuvette group lid 31 of different models with varying lengths of the stoppers 31a in the lid 31 of the cuvette group, or by producing different high cuvette groups 32. Furthermore, the walls of the stoppers 31a present in the cuvette group lid 31 can be made impermeable to light, whereby the light can only pass through the transparent bottom plane 31b in the stoppers 31a of the cuvette group 32 lid 31.

Thanks to the present construction, errors in the height of the liquid column due to transfers with a pipette cause splashing of liquid in the form of drops 35 on the inner walls of the cuvette group 32, not errors in the length of the light path.

If the surface of the liquid nozzle present in the cuvettes of the cuvette group is curved or slanted, this can cause errors in the measurement result when using a photometer that works according to the vertical measurement principle. When the cuvette group 32 is connected with the cuvette group 32 lid 31, the bottom plane 36 in each cuvette 32 is parallel to the bottom plane 31b in the plug 31a on the cuvette group lid 31 in a similar way. In this way, the light travels vertically through the parallel surface planes and the liquid soil between them, which is why the impact of the above-mentioned errors in the measurement result disappears.

Sometimes bubbles 37 are formed on the free liquid surface in connection with shaking or using a pipette. Such bubbles can disturb the photometric measurements when the measurement takes place according to the vertical measurement principle and the light passes through the bottom plane 36 in the cuvette 32a of the cuvette group 32 and the following liquid column, and finally passes through the free surface of the liquid and the air to the detector 40. When the cuvette group 32 is closed with the cuvette group lid 31, the bottom plane 31b in each stopper 31a on the cuvette group 32 lid 31 is pressed somewhat below the free liquid surface 34- in the cuvettes 32a that correspond to the stoppers 31a in the cuvette group 32 lid 31. This moves any bubbles 37 on the liquid surface to the free liquid surface between the inner wall of the cuvette group 32 cuvette 32a and the outer wall of the plug 31a in the cuvette group 32 lid 31.

The errors described above can, if necessary, also be corrected so that instead of the lid in the cuvette group 32, the protected tip of the detector 40 is inserted into each cuvette 32a in the cuvette group 32 so that it reaches somewhat below the liquid surface 34.

According to Beer's law, the liquid's absorption is directly and linearly related to the length of the light path in the cuvette. When measuring in a. cuvette group 32 where the lid 31 is not used, in the photometer which functions according to the vertical measurement principle, the light lines in the cuvettes 32a of the cuvette group 32 are the same as the heights of the liquid solutions in the cuvettes 32a, which heights are in turn directly and linearly related to the liquid volume that is transferred by pipette to the cuvette. If the reagent is transferred with the pipette in too small an amount, provided that the sample amount is measured correctly, the light path in the cuvette has become shorter, and the absorption increases per unit of measurement light path in the cuvette. If too much reagent is added, the absorption decreases per unit of measurement light path in the cuvette. When measuring with the photometer operating according to the vertical measurement principle without using the lid 31 of the cuvette group 32, which, as described above, makes the light path in the cuvettes 32a of the cuvette group 32 constant, a possible error with the reagent or the transfer of the reagents with a pipette causes no error in the absorption of the reaction mixture . Only if the sample is pipetted incorrectly will errors occur in the absorption of the reagent mixture. In a photometer with several channels which works according to the vertical measurement principle, the detectors 40 are in the immediate vicinity of the front amplifier 41 at the measuring end of the photometer or almost at this. Hereby, error signals cannot occur due to long transmissions from the detectors 40 to the front amplifier. At the measuring end of the photometer, the cuvette group 32 setting device 42 lifts the cuvette group 32 upwards towards the surface plane 43 of the measuring end. When the lifting movement has stopped, this surface plane forces the cuvette group cover 31 tightly against the cuvette group 32. This guarantees that the cover 31 of the cuvette group 32 is securely in place, whereby e.g. e.g. the light path in each cuvette 32a in the cuvette group 32 is the same length. In each light-conducting fiber 44 that reaches the measuring end, light of the same or different wavelength can be guided. With this method, can the cuvettes 32a in a cuvette group 32 measure with the same or different wavelength?

The invention is not limited to the examples given above, but can be varied in many ways within the framework of the patent claims.

Claims (17)

1- Procedure for automatic reading and determination of results from virological, bacteriological and hematological reactions or for spectrophotometric measurement and determination of results from chemical color reactions on the basis of a change in light intensity of a certain magnitude caused by a change in the reproducibility of light, characterized by the fact that the cuvette, row of cuvettes or group of cuvettes present in their place at the time of the measurement, is guided through the liquid dipstick in place in each cuvette (C, 10) designed for reading and measurement and adjacent cuvette base, the light (2, 8) in the reading device to go in the direction of the longitudinal axis in each cuvette (C, 10) from the light source on one side of the cuvette (C, 10) to the detector (3, 14) on the other side of the cuvette, whereby, when the light travels in the longitudinal axis of the cuvette direction, results from serological, bacteriological or haematological reactions or color reactions can be read from folds, fading etc. on the bottom of the cuvette or cuvettes in place, or in the liquid soil if they have not sunk to the bottom, and which have caused a change, or on a color change in the liquid in the cuvette or cuvettes which causes a change in the permeability to light, on the basis of a certain depending on this change in the intensity of the light. 2. Method according to claim 1, characterized in that at each cuvette (C, 10) there is a light source or a common light source over all cuvettes, and preferably a detector (3) for each cuvette. 3. Method according to claim 1, characterized in that light sources (2) are arranged in a row in the reading device on the holder (1) and a detector (3) corresponding to each light source and that the holder (1) is arranged to be pushed from position by a cuvette row to another or that the cuvette rack can move while the holder is held in place, whereby the cuvettes (C) are read or measured in one row at a time. 4. Method according to claim 1, characterized in that during and for measurement each cuvette (32a) in the cuvette group (32) is closed with the lid (31) so that the bottom plane (31b) of each stopper (31a) in the lid (31) is pressed under it free liquid surface (34) in the cuvette (32a) corresponding to the stopper (31a) in the cuvette group (32), or that the detector element (40) protected tip is installed in each cuvette (32a) in the cuvette group (32) below the free liquid surface (34) in each cuvette (32a) in the cuvette group (32) at the point through which the light from the liquid continues to the detector (40). 5. Device for carrying out the method according to claim 1, characterized in that the device includes cuvette groups (16^) that can be placed in a cuvette stand (15), whose stationary or removable cuvettes (18) have the same relative position as the detectors and corresponding light sources in the measuring device, and that the measuring opening (21) of the cuvettes (18) is suitably surrounded on the outside by a cylindrical protective part or edge (22). 6. Device according to claim (5), characterized in that the cuvettes (18) in the cuvette group (16) can be closed at the same time with a lid (20) whose stoppers have the same relative position as the cuvettes (18) in the cuvette group (16). 7. Device according to claims 5 and 6, characterized in that the lower part (23) of the cuvette group's (16) cuvettes (18) has the shape of a blunt cone to facilitate alignment of the cuvette group's (16) cuvettes (18)... 8. Device according to claims 5-7, characterized in that there are one or more screens (24) in the longitudinal direction of the cuvette (18) on the inner wall of the cuvette (18). 9. Device according to claim 5, characterized in that the bottom of the used cuvette (C, 10) or of each cuvette in the cuvette group is concave on the inside, and flat on the outside. 10. Device according to claim 5, characterized in that the bottom of the cuvettes (18) of the cuvette group (16) is flat. 11. Device according to claim 5, characterized in that the cuvette group stand (15) has a projection (25) that fits into a recess (26) or an opening in the cuvette group's (16) holding plate (17) so that the cuvette group (16) can only be placed in the cuvette rack (15) in one path Iling. 12-. Device according to claim 5, characterized in that in the holding disc (17) of the cuvette group (16) there is a code (27) with which the cuvette group (16) can be identified in the measuring device and/or visually. 13. Device according to claim 5, characterized in that the cuvette group stand (15) is thermostatically controlled. 14. Device according to claim 5, characterized in that the device includes a cover (31) which consists of a continuous disc in which hollow, downward-directed plugs (31a) are formed, the bottom of which is made up of a transparent bottom plane running in the direction of the cover disc (31b) at the same distance from this, and that the outer diameter of the stoppers (31a) at their bottom plane (31b) is smaller than the inner diameter of the cuvettes (32a) corresponding to the lid (31) in the cuvette group (32). 15. Device according to claim 14, characterized in that the plugs (31a) of the lid (31) are cylindrical. 1.6. Device according to claim 14, characterized in that the plugs (31a) of the lid (31) have the shape of a blunt, downwardly tapering circular cone. 17. Device according to claim 14, characterized in that the side walls of the plugs (31a) in the lid (31) are completely or partially permeable to light.