OF THE TESTES AND SEMINAL FLUIDS. 



885 



simple vesicles, but have a sacculated glandular character; and their secre- 

 tion seems to be of a mucous nature. Into the same part of the urethra is 

 discharged the secretion of the Prostate Gland, which is poured forth by a 

 number (15-20) of separate ducts into a depressed fossa on either side ; of 

 the nature of this secretion scarcely anything is known ; and it can be only 

 surmised that its use, like that of the fluid of the vesicular seminales, is to 

 dilute the seminal fluid, and to give it such an increase of bulk that it may 

 be more effectually conveyed within the female passages. It seems probable, 

 indeed, that a certain dilution of the fluid secreted by the testes may be a 

 condition of its power of fecundation ; since it has been ascertained by Mr. 

 Newport, that too copious an application of spermatozoa to an ovum is abso- 

 lutely unfavorable to their action. That in some way or other both these 

 glandular bodies serve as accessory organs of generation, may be inferred 

 from the fact, that in animals which have only a periodical aptitude for pro- 

 creation, they undergo an alternate increase and decrease, corresponding 

 with the periodical enlargement and diminution of the testes themselves. 

 The essential peculiarity of the Spermatic fluid, however, consists in the 

 presence of a large number of very minute bodies, the spermatozoa, which, 

 from their usually remaining in active motion for some time after they have 

 quitted the living organism, have been erroneously considered as proper Ani- 

 malcules. The Human Spermatozoon (of which representations are given 

 in Plate I, Fig. 1 ; whilst some of the principal forms in other animals are 

 shown in Fig. 308) consists of a little oval flattened " head " 5 p in length, 

 an intermediate portion 6 p in 

 length, from which proceeds a 

 long filiform "tail" gradually 

 tapering to the finest point, of 

 50 JJL in length. The whole 

 is perfectly transparent ; and 

 nothing that can be termed 

 " structure " .can be satisfac- 

 torily distinguished within it. 1 

 Its movements are principally 

 executed by the tail, which has 

 a kind of vibratile undulating 

 motion; they may continue for 

 many hours after the emission 

 of the fluid ; and they are not 

 checked by its admixture with 

 other secretions, such as the 

 urine and the prostatic fluid. 



m . . 1. Spermatozoon of the frog. 



In us, in cases of nocturnal 2 . triton. 



emission, the Spermatozoa may 3. fim-h. 



not unfrequently be found ac- 4 - nd i-.uouse. 



i ii. u xu 5. hedgehog. 



tively moving through the 6 sh.ep. 



urine in the morning ; and a . Head with nucleus, b. Body. c. Tail. 



FIG. 308. 



1 The characteristic forms of the spermatozoa of the various classes of the verte- 

 brata, are beautifully represented by Scbweigger-Seidel in Max Sehultze's Mikroskop. 

 Anat., Bd. i, p. o09. He describes each spermatozoon as consisting of a head, body, 

 and tail the latter, as in some tritons, having a membrane attached to it, which per- 

 forms undulatory movements. Grohe (Virchow's Archiv, Bd. xxxii, p. 401) attrib- 

 utes the movements of the spermatozoa to the contractile protoplasm contained in 

 the "head" of the zooid ; Bizzozero to that in the cilium or tail. See also v. Lava- 

 lette St. George, Art. Testes, in Strieker's Hum. and Comp. Histology, Syd. Soc. 

 Transl., 1872, vol. ii, p. 14'J. 



