244 



O. ISHII. 



The Length of the Period of Gestation in the Guinea Pig. 



On the basis of our observations we can give the following 

 statistical data concerning the length of the period of pregnancy 

 in the guinea pig. 



The shortest period was 61 days; but those young animals 

 which are born 61, 62 and 64 days following copulation show a 

 certain lack of development; they are really born prematurely 

 and in the majority of cases they soon die, although they may 

 be able to survive. Those born 66 days after copulation usually 

 lived and continued to grow, but those born from 67 to 69 days 

 following copulation show the maximal development after birth ; 

 these have the best chance to develop into absolutely healthy, 

 perfect animals. We may therefore conclude that 68 days is the 

 regular period of gestation in the guinea pig. 



Separation of the Symphysis Pubis in the Guinea Pig at the End 

 of Pregnancy, at the Time of Birth and During the 

 Period Directly Following Birth. 



Through examination with the finger we discern in the guinea 

 pig a gradual separation of the symphysis pubis which begins 

 about 6 1 to 63 days after copulation and increases as the time 

 of labor approaches to a width of 7 to 8 millimeters or more; 

 but within one or one and a half days after birth the symphysis 

 pubis assumes again its normal condition. The following table 

 shows the time when the separation becomes apparent : 



The length of time from the beginning of the separation of the 

 symphysis to the onset of labor is shown on the following table: 



