264 EMBRYOLOGICAL METHODS. 



If the method of washing out is adopted, it is best to use a good 

 rubber bulb attached to a glass tube which has been drawn out 

 finely enough to pass into -the oviducal opening. Kolliker used 

 Miiller solution or weak osmic acid for injection, collecting the 

 fluid in a series of watch glasses ; J. P. Hill uses solid crystal dishes, 

 which can easily be examined under a stereoscopic binocular 

 microscope. As a fluid for washing out Hill's picronitric osmic 

 (vide infra), weak formalin, or weak osmic acid are probably as 

 good as anything. The success of this injection method depends 

 on the amount of mucous in the tuba and on the condition of the 

 folds in its mucosa ; if the eggs are not found after the injection, 

 the walls of the tube may be opened up with scissors and the lining 

 scraped away with a small scalpel ; the mucus thus procured may be 

 diluted with a little indifferent fluid and examined on a slide under the 

 microscope. Both operations of injection or of opening the tuba 

 may succeed with comparatively large animals like the rabbit and 

 dog. It is practically impossible to slit open the tuba of the cat. 



In cases where the subject is small, as, for instance, the mouse, 

 it is necessary to preserve the whole oviduct and use a fixative 

 sufficiently penetrative to act quickly. Even with the guinea-pig 

 the lumen of the tube is so small that it is difficult to remove the 

 ova ; we consider that attempts to press out the contents of the 

 tubes are dangerous. In such cases it seems better to cut the 

 tube into lengths with a razor and to fix whole (vide infra). BISCHOFF 

 in his study on the guinea-pig (Giesson, 1852), and BALLOWITZ 

 (Arch. Anat. Physiol, 1883) both resorted to the method of squeezing 

 out the contents of the tubes. 



When found the ova are picked up with the point of a cataract 

 needle or a scalpel, on a piece of black paper cut to a point, or 

 with a pipette, and either examined fresh in the peritoneal fluid or 

 blood serum of the animal, or in Kronecker's or other artificial 

 serum media, or better fixed immediately. 



In the case oi a large animal such as the rabbit, the same doe may be 

 made to serve for two observations, at some hours' or days' interval. A 

 longitudinal incision of 8 to 10 centimetres' length is made on the 

 median or a lateral line of the abdomen ; an assistant keeps the intestines 

 in their place ; a ligature is placed at the base of one of the uterine 

 cornua, beneath the neck, and a second ligature around the mesometrium 

 and mesovarium. The ovary, the tuba, and the cornu of that side are 

 then detached with scissors. The abdomen is then closed by means of 

 a few sutures passing through the muscle -layers and the skin. The 

 animals support the operation perfectly well, and the development of 

 the ova of the opposite side is not in the least interfered with. When it 



