292 CHAPTER XXV. 



and look for the ova under the microscope by transmitted 

 light. 



Another method, employed by KOLLIKER, consists in in- 

 jecting solution of MULLER 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 l)e 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 niesometrium 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 is desired to study these the animal may 

 be killed, or may be subjected to a secondary 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 

 MULLEK, or O'l peNcent. solution of osmic acid, or KLEINKN- 

 BERG'S picro-sulphuric acid, or nitric acid, or acetate of 

 uranium solution. With a small scalpel a longitudinal in- 

 cision is made on the surface of the ovular eminence, not 

 passing deeper than the muscular layer ; the underlying 

 uterine mucosa is then gently dilacerated with two pairs of 

 small forceps, and the ovum set free in the liquid. 



