OBSERVATIONS ON THE SEXUAL CYCLE OF THE 



GUINEA PIG. 



O. ISHII, 



PATHOLOGICAL LABORATORY OF THE WESTERN PENNSYLVANIA HOSPITAL, 



PITTSBURGH, PA. 



In the following work, which was undertaken at the suggestion 

 of Professor Leo Loeb, my aim has been to correlate the micro- 

 scopical and experimental analysis of the sexual cycle which this 

 author had previously made and further studies which he had 

 planned at that time with a careful study of the cyclic changes as 

 far as they are accessible to the naked eye. These observations 

 were made at the breeding establishment of Miss A. E. C. 

 Lathrop, in Granby, Mass., during the years 1913 and 1914. l 



THE THREE STAGES OF MENSTRUATION AND HEAT. 



i . Prcestrum. This period continues for one to one and a half 

 days, during which time the external genital organs become 

 congested and swollen and a slight serous secretion is noticeable. 

 This secretion, while in some instances turbid or viscid, is in 

 the majority of cases more or less transparent; while, as before 

 said, this period averages one to one and a half days, in some 

 instances it may continue for two or three days or more. In the 

 last 4 or 5 hours toward the end of this period a maximum in 

 these changes is reached. This is followed by the period of heat. 

 The duration of the procestrus period is indicated on the following 

 table. Ninety-four (94) animals served for this observation. 



1 Accidental conditions greatly delayed the publication of this paper. In the 

 meantime there has appeared a study of Stockard and Papanicolaou on the oestrous 

 cycle of the guinea pig. Notwithstanding this long delay in publication, we believe 

 that our observations present new facts of interest and are worth recording. 



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