8PERMATOZOIDS. 329 



seminales, or after ejaculation, the spermatozoids are invari- 

 ably in active motion. 1 



The semen thus developed and mixed with the various 

 secretions before mentioned is found during adult life and 

 even at an advanced age ; and, under physiological condi- 

 tions, it contains innumerable spermatozoids in active move- 

 ment. But if sexual intercourse be frequently repeated at 

 short intervals, the ejaculated fluid becomes more and more 

 transparent, homogeneous, and scanty, and may consist of a 

 small amount of secretion from the vesiculse seminales and 

 the glands opening into the urethra, without spermatozoids, 

 and consequently deprived of fecundating properties. 



In old men, the seminal vesicles may not contain sperma- 

 tozoids ; but this is not always the case, even in very advanced 

 life. Instances are constantly occurring of men who have 

 children in their old age, in which the paternity of the 

 offspring can hardly be doubted. Duplay, in 1852, examined 

 the semen of a number of old men, and found, in about half 

 the number, spermatozoids, normal in appearance and quan- 

 tity, though, in some, the vesiculse seminales contained either 

 none or very few. Some of the individuals in whom the 

 spermatozoids were normal were between seventy-three and 

 eighty-two years of age. a More recently, M. A. Dieu has 

 investigated the same question. In his conclusions, adding 

 to his own observations the fifty-one cases noted by Duplay, 

 he gives the following results, in one hundred and fifty-six 

 old men : 



1 KOLLIKER, Elements d'histologie humaine, Paris, 1868, p. 678, et seq. 



2 DUPLAY, Recherches sur le sperme des vieillards. Archives generates de me- 

 decine, Paris, 1852, 4 e serie, tome xxx., p. 897. 



Duplay seems to have been the first, except Wagner, to have demonstrated 

 microscopically the presence of spermatozoids in the vesiculae seminales of old 

 men, but others had found a liquid like the semen in the vesicles and testicles. 

 Duplay cites a case of this kind reported by Timmius, in an old man of ninety- 

 four. Wagner (Elements of Physiology, London, 1841, p. 7) makes the follow- 

 ing statement : " I have constantly found seminal animalcules in the fluid of the 

 testis of very aged men ; it is only among weakly and decrepid individuals that 

 the procreative faculty is really lost." 



