232 CHARLES R. STOCKARD AND GEORGE N. PAPANICOLAOU. 



from rats did not influence their sexual instincts or ability to 

 copulate, but decidedly impaired the power of the male to fertilize 

 the female. 



Sobotta ('95) also has studied the formation of the vaginal 

 plug in the mouse and found it present after every copulation. 

 Histologically it consists of an homogeneous mass which is 

 surrounded by an envelope of vaginal epithelium. Spermatozoa 

 are more abundant in the central mass at its upper end or that 

 portion near the uterus as the plug lies in the vagina. He con- 

 firms the observations of Tafani regarding the fate of the vaginal 

 plug, finding that its surface gradually becomes soft and loose 

 and the entire mass falls out of the vagina about twenty to thirty 

 hours after copulation. Sobotta states that the vaginal plug 

 in the guinea-pig falls out much sooner than in the mouse, being 

 eliminated from the vagina within from four to nine and a half 

 hours after copulation. The longer interval is approximately 

 correct. He claims to have at times observed another copulation 

 following the expulsion of the first vaginal plug. 



Camus and Gley ('96) studied the coagulation process in the 

 formation of the vaginal plug. They claim coagulation to be 

 due to the influence of a prostatic enzyme, "vesiculase," upon 

 the secretion of the seminal vesicles. The action of the prostatic 

 enzyme is specific towards the seminal vesicle secretion of any 

 rodent. The prostatic enzyme of a rat will coagulate the seminal 

 fluid of a guinea-pig and vice versa. 



Rubaschkin ('05) returns to the old opinion of Reichert, 1861, 

 in claiming that the vaginal plug is not a constant formation in 

 the guinea-pig following copulation. His statements are as 

 follows: Bei der Maus (Sobotta), und nach Bischoff und Hensen 

 auch bei Meerschweinchen bildet sich nach dem Coitus ein 

 charakteristischer Vaginal-pfropf, der auf einen vorausgegan- 

 genen Coitus hinweist. Ich muss hier die Beobachtungen von 

 Reichert bestatigen, dass beim Meerschweinschen ein solcher 

 Vaginalpfropf sich meistens nich bildet. Von aussen konnte ich 

 einen klaren Pfropf in der Vagina niemals erkennen; in einigen 

 Fallen liessen sich einige Schleimstreifen bemerken, die aber 

 ganz unregelmassig und nicht immer zu Tage traten. In seltenen 

 Fallen wurden nach dem Secieren Vaginalpfropfe gef linden, 



