462 PRACTICAL DIRECTIONS. [APP. 



dish. Carefully stretch out the oviduct by cutting 

 the tissue which binds it, and separating it from 

 the uterus, taking care to obtain its whole length, 

 lay it upon a glass slide. 



With the aid of a lens it is frequently possible to 

 distinguish the ovum or ova, through the wall of the 

 oviduct. In this case cut a transverse slit into the 

 lumen of the duct with a fine pair of scissors a little 

 to one side of an ovum ; press with a needle upon 

 the oviduct on the other side of the ovum, which will 

 glide out through the slit, and can be with ease trans- 

 ported upon the point of a small scalpel, or what is 

 better spear-headed needle. In case the ovum cannot 

 be distinguished in the oviduct by superficial obser- 

 vation, the latter must be slit up with a fine pair of 

 scissors, when it will easily be seen with the aid of an 

 ordinary dissecting lens. 



B. Treatment of the ovum. 



The ovum may be examined fresh in salt solution, 

 it is however more instructive when preserved and 

 stained in the following manner. 



a. Immerse it in a \ p.c. solution of osmic acid for 

 5 or even 10 minutes, transfer it thence to 

 the picrocarmine solution described above (I). 

 After staining the ovum should then be washed 

 in distilled water and placed in a weak solu- 

 tion of glycerine in a watch-glass half gly- 

 cerine, half water. It should be allowed to 

 remain thus under a bell jar for several days 

 (7 to 14 or longer) in a warm room until the 

 water has evaporated. By this means shrinkage 

 and distortion are avoided, the glycerine becoming 



