In the biology of the reproduction and, more specifically, in the practice of the artificial insemination, techniques of seminal liquid sedimentation by density gradient are commonly used in order to gather the spermatozoa below liquid phases of different densities.

Alternately, the selection of the moving spermatozoa by the swim-up technique may be resorted to, wherein the spermatozoa move upwards and are collected in the upper culture medium.

In both cases the spermatozoa are picked by the operator manually by suction through a Pasteur pipette or a syringe connected to a probe of suitable length, with the danger of contaminating the already formed layers because of their mixing or due to the introduction of such pipette or probe.

The present invention seeks to solve such a problem by providing a test tube which is equipped with means inhibiting undesired mixing and contamination of the layers during the suction or deposition of the sample

by the operator.

This is achieved according to the invention by providing a test tube equipped wit: a) a fixed small probe extending along the inner wall of the test tube up to the bottom of the same in order to allow the desired layers to be either deposited or sucked by a Pasteur pipette or a syringe or the like connected or not to another small probe of lower diameter; b) a spiral protrusion on the inner wall of the test tube which allows said Pasteur pipette or a syringe to be firmly supported at the desired height without causing a strong liquid flow. Actually, the liquid to be sucked or deposited will flow downwards along the inclined spiral so as to avoid undesired mixing and contamination.

A better understanding of the invention will ensue from the following detailed description with reference to the accompanying drawings which show by way of a not limiting example a preferred embodiment of the invention. In the drawings: Fig. 1 is an exploded view of the test tube with relative screw cap; Fig. 2 is a section view according to the plane I-I of

the test tube of Fig. 1.

With reference to the figures, an usual test tube consists of a plastic or glass tube 4 provided with a conical bottom 6 and at its upper mouth 8 with a screw thread 10 allowing a screw cap 12 to be screwed thereon.

According to a first feature of the invention such test tube is provided along its inner wall with a fixed small probe 14 extending from near the mouth 8 up to near the rounded bottom 6 where it is provided with a suitable goose bill 16, as can be seen from Fig. 2. The diameter of such small probe is much lower than that of the test tube but large enough to receive a further flexible probe. By way of example, the diameter of the small probe is 1-2 mm while the test tube has an inner diameter of 15 mm.

Advantageously, such small probe 14 is provided at the upper side with a Luer cone for a syringe 18 so as to help the operator. Preferably, the small probe is made in one moulding piece with the test tube. Alternately, a flexible small probe having the above-mentioned features may, however, be secured to the test tube by adhesives or other known means.

According to another feature of the invention, the inner surface of the test tube is provided with a spiral protrusion 20 essentially extending for its whole length. Such spiral protrusion provides a support for the Pasteur pipette or the syringe at the desired height and avoids any oscillation and causes a

flow which is tangential to the formed layers and not perpendicular thereto with the risk of a not controlled contamination (vertical withdrawal) A test tube having the features mentioned above fully satisfies the requirements of the operator both in the sedimentation technique by density gradient and the swim-up technique.

The way for use is very easy.

By the first technique, the solution (Percoll, glucose or sucrose, etc.) having lower density is deposited by a syringe through the fixed small probe, and in succession the other solutions having higher density are deposited still through the same small probe.

The sample to be deposited as a layer above the formed gradients is then taken by a Pasteur pipette or a syringe. The sample is then carefully deposited at the intersection between the outer wall of small probe 14 and spiral 20 within the test tube near the surface of the uppermost deposited layer.

After centrifugation, a suitable amount of pellet is sucked by small probe 14 or, if Percoll is used, the whole supernatant is sucked and the desired amount of pellet is preserved. In the other cases, the desired layers are sucked by laying the Pasteur pipette or a syringe on spiral 20.

In the selection of the moving spermatozoa by the swim-up technique, the selected medium is deposited by small probe 14 and then the seminal liquid as such or a treated one is deposited by the same. After 1-2

hours the supernatant is sucked by laying the pipette on the spiral 20 at the desired height.

From the foregoing the advantages of using the test tube according to the invention are self-evident.

The fixed small probe extending to the bottom of the test tube allows the liquid layers having a biological density to be formed much more quickly without mixing the layers being formed with one another, thus avoiding the risk of inadvertent oscillations or sudden accelerations caused during the deposition. In addition, the system prevents the already deposited liquid layers from being crossed to form underlying layers having higher density.

During the suction of any supernatant and the careful deposition of upper layers of medium or biological liquids the particular spiral protrusion within the test tube allows the Pasteur pipette or the syringe to be firmly laid at the desired height without creating strong liquid flows. The liquid to be either sucked or deposited will flow of course along the inclined spiral so as to avoid undesired mixing and contamination.

The present invention is described and illustrated according to a preferred embodiment thereof, however, it should be understood that anyone skilled in the art can make modifications and/or equivalent replacements without departing from the scope of the present industrial invention.