230 CHARLES R. STOCKARD AND GEORGE N. PAPANICOLAOU. 



described it as a Pfropf (plug), formed by the coagulation of the 

 secretion from the seminal vesicles and serving to fill the vagina 

 and prevent the flowing out of the sperm after copulation. 



Bischoff, in 1852, verified the observations of Leuckart and 

 accepted his conclusions regarding the role of the vaginal plug in 

 the copulation process. Reichert, 1861, differed with these two 

 original descriptions in failing to find the formation of a vaginal 

 plug after every copulation, and concluded that its presence was 

 not a general phenomenon. Later, however, Hensen in 1876 

 brought new evidence confirming the observations of Leuckart 

 and Bischoff. 



Landwehr, in 1880, examined the seminal vesicles and found 

 their secretion to contain twenty-seven per cent, of fibrinogen to 

 which its coagulation reaction is due. Coagulation may occur 

 as soon as the secretion of the seminal vesicles comes in contact 

 with a small amount of blood. 



Heron-Royer, 1881, observed the vaginal plug in Pachyuromys 

 dnprasi, but gave no satisfactory explanation of its formation. 

 According to him the vaginal plug was formed in the vagina 

 before copulation and was pulled out or loosened by the hooks 

 on the penis during the act of copulation. These observations 

 were entirely contrary to all earlier records, according to which 

 the plug is formed after copulation and falls out some hours later. 

 Blanchard made histological examinations of the vaginal plugs 

 collected by Heron-Royer and found them to consist of two parts, 

 a central, partie centrale, composed chiefly of great numbers of 

 spermatozoa, and a peripheral part, couche corticale, formed of 

 hardened mucus. 



Lataste, in 1882, after examinations of the vaginal plug in 

 the same species, Pachyuromys duprasi, came to quite different 

 conclusions. He states that the vaginal plug, bouchon vaginal, 

 as he termed it, is not formed as Heron-Royer claimed, before 

 copulation, but immediately after, and in the same way as was 

 known for other rodents. Regarding its function he accepted 

 the old opinion of Leuckart that it serves to prevent the spermato- 

 zoa from flowing out of the vagina after copulation. He also 

 mentions an instance in which a vaginal plug-like formation was 

 found when there had been no previous copulation. From our 



