SEXUAL CYCLE OF THE GUINEA PIG. 



243 



is mostly transparent, but sometimes turbid. It continued for 

 3 to 8 days in my observation; then the external genitalia 

 returned to a normal condition. 



Some authors suppose that the diagnosis of the menstrual 

 secretion is very difficult in the guinea pig; however careful 

 observation has shown me that the diagnosis can be readily 

 made and hardly misinterpreted. 



Diagnosis of Pregnancy about 14 to 15 Days after Copulation. 



About 14 or 15 days after copulation we can correctly determine 

 the success or failure of the impregnation. If at that time the 

 external genitalia are in a normal condition we may almost always 

 assume a successful pregnancy. If, on the other hand, there 

 should be within that time a noticeable swelling of the external 

 genitalia, accompanied by secretion, this may in all cases be 

 taken as an indication of failure. As we have stated above, 

 the same phenomenon may be present, perhaps in a milder form, 

 at this period of pregnancy, but this is a very rare occurrence; 

 and as a general rule in the case of failure (early abortion) the 

 secretion and swelling is much more marked. 



The Sexual Cycle in Cases of Early Abortion. 



In cases of early abortion I found the period of heat in some 

 cases somewhat accelerated and more irregular than in normal 

 animals. 



DlOESTRUM. 



As shown in the table, the heat period may appear as early 

 as 12^2 or J 3^ days after copulation. In control cases the 

 shortest period observed was 14^ days and this occurred only 

 once; and, as I stated above, I believe that in normal cases 15 

 days represents the minimum and that the shorter periods are 

 usually found in cases of abortion. 



