BABBIT. 261 



point of a scalpel, a cataract needle, or a small pipette. They 

 may be examined in the peritoneal fluid of the mother, if the 

 animal has been killed, or in its aqueous humour, or in 

 amniotic liquid, or in blood serum, or in Kronecker's or other 

 artificial serum. 



If you have not been able to find the ova with the lens or 

 the microscope, scrape off the epithelium of the tubal mucosa 

 with a small scalpel, mix it with a little indifferent liquid, 

 and look for the ova under the microscope by transmitted 

 light. 



Another method, employed by Kolliker, consists in in- 

 jecting solution of Miiller or weak osmic acid into the oviduct 

 by means of a small syringe, and collecting the liquid that 

 runs out in a series of watch-glasses, in which the ova can 

 very easily be found by the microscope. 



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 mesome- 

 trium 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 sup- 

 port the operation perfectly well, and the development of the ova of the 

 opposite side is not in the least interfered with. When it is desired to study 

 these, the animal may be killed, or may be subjected to a second laparotomy 

 if it be desired to preserve it for ulterior observations. 



During the fourth, fifth, and sixth days after copulation the 

 ova of the rabbit are free in the uterine cornua ; they are 

 easily visible to the naked eye, and may be extracted by the 

 same manipulations as those of the tubes. After the sixth 

 day they are at rest in the uterus, but have not yet contracted 

 adhesions with the mucosa, so that they can still be extracted 

 whole. At this stage the parts of the cornua where the ova 

 are lodged are easily distinguishable by their peculiar aspect, 

 the ova forming eminences of the size of a pea. The cornua 

 should be cut up transversely into as many segments as there 

 are eminences, care being taken to have the ova in the centre 

 of the segments. You then fix each segment by means of 

 two pins on the bottom of a dissecting dish, with the meso- 

 metrial surface downwards and the ovular eminence upwards. 

 The dissecting dish is then filled up with serum or liquid of 



