246 



O. ISHII. 



As our table shows, in 2 out of 20 guinea pigs no heat at all 

 was observed at this period. There was evidence pointing to the 

 conclusion that the heat is less vigorous at this stage than in 

 the, normal menstrual period. On the other hand the heat seems 

 perhaps to be of a somewhat longer duration at this period as 

 shown in the following table: 



We find therefore that in about one third of the guinea pigs 

 at this period the average duration of heat was 12 to 13 hours, 

 while in normal animals the heat continues for that length of 

 time only in a small minority of cases. Whether or not heat 

 occurs in the period directly following parturition depends upon 

 the duration of the period of gestation as shown in the following 

 table : 



Duration of Pregnancy. 



+ coming in heat; not in heat. 



This table shows that heat does not occur in the period directly 

 following parturition in cases in which the duration of pregnancy 

 was less than 66 or 67 days. In cases in which the duration of 

 pregnancy was less, birth occurred prematurely and the phe- 

 nomena of the puerperium had not yet fully developed at the 

 time of the completion of labor. If in cases of parturition 

 occurring 61 or 62 days after copulation the first heat following 

 parturition would take place 6 or 8 days later, the first heat 

 would correspond to a typical puerperal heat, provided the 

 duration of pregnancy would have been 68 or 69 instead of 

 61 days. 



