238 



O. ISHII. 



On the basis of these observations it may be reasonably said 

 that the average length of this period in an animal of normal 

 physical condition is from one to one and a half day, but after 

 puerperium, or in case of weakness or of pathologic conditions, 

 a shortening or prolongation may be brought about. 



2. (Estrus, or Heat. The approach of this period is made 

 apparent by excessive menstrual secretion during the last 4 or 5 

 hours of proffistrum. This continues for 6 or 7 hours of the 

 oestrus period. This is followed by the" secretion of a small 

 quantity of moisture which may be just noticeable, or during the 

 last 3 or 4 hours of the oestrus period menstrual secretion may 

 be lacking altogether; still heat is present in this period. 



I give the following data as to the length of period of heat: 



As can be seen from the above figures, from 8 to n hours is 

 the average length of the heat period in the healthy animal. I 

 found those guinea pigs in which the periods were longer (12 to 

 14 hours) or shorter (5 to 6 hours) to have been lacking in vigor 

 or to have shown abnormal physical conditions. In the normal 

 animal I feel justified in claiming, on the average, 9 to n hours 

 as the correct length of this period in the normal guinea pig. 



3. Metcestrum. This is the period following the oestrus period 

 and might be considered as the period of recovery from the 

 cestrous changes. The length of this period depends almost 

 wholly on the condition of the animal. In the normal animal 

 2 ^ to 3 days are required until the normal condition is re- 

 established. From the figures that follow it will be noticed 

 that the length of this period varies from i^ to 5 days, but my 

 observations have convinced me that where the recovery is 

 shorter or longer than the average period, the animal is not in a 

 normal healthy condition. 



Length of Metoestrus Period. 



