EMBRYOLOGY 365 



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

 serum media, or better fixed immediately. 



Van der Stricht method of obtaining Ova from Fallopian Tube of 

 Dog. Dissect out tube and stretch straight. Divide across into 

 two parts. Then with gentle pressure from scalpel, squeeze along 

 the length of the segment, so as to express the contents on a clean 

 slide. A drop of viscid fluid exudes in which should be the ova. 

 Fix by osmic vapour method, by inverting over mouth of osmic 

 bottle. The fluid will coagulate and the block may be cut and 

 transferred to the desired fixative. 



In the case of 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 

 medial or a lateral line of the abdomen ; an assistant keeps the intes- 

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

 eornua, beneath the neck, and a second ligature around the meso- 

 metrium and mesovarium. The ovary, the tuba, and the eornu 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 sub- 

 jected to a secondary laparotomy if it be desired to preserve it for 

 ulterior observations. This method, however, cannot be carried out in 

 England without a licence. 



This procedure was also adopted by Hartmann in his study on 

 Didelphys (vide infra). 



803. Fixation of the Isolated Ova. These can be fixed in a 

 chrome-formalin fluid of some kind : Miiller-formol, Helly, 

 Zenker-without-acetic acid and formol are indicated. Eggs may 

 be left in one of these fluids overnight, then washed in distilled 

 water and transferred either to 1 per cent. OSO4, or to some 

 chrome-osmic fluid, this to preserve the fat. The chrome fixation 

 win form insoluble compounds with lipoids, but less so with fats 

 of the type of olein. It seems likely that the fixation technique 

 of Champy-Kufl, of Schridde and of Murray (see §§ 691 et seq.) 

 will be of great value. 



For a study of the Golgi elements the methods of Cajal and Da 

 Fano and of Ludford are worthy of trial, but rather more difficult 

 to work than chrome-osmic or chrome-formol techniques. Where 

 there may be a difficulty of penetration chrome-formol fluids will 

 be found better than chrome-osmium. A perusal of the sections 

 on Mitochondria and Golgi apparatus will provide suggestions for 

 the treatment of the early stages in mammalian development. 

 Van Beneden {Arch, de Biol., 1880, p. 149) brings the living ovum 

 into a drop of 1 per cent. OSO4 on a slide, and thence into a solution 

 of Midler. After an hour the liquid is changed, and the whole is 

 put into a moist chamber, where it remains for two or three days. 

 It is then treated with glycerin of gradually increasing strength, 



