480 URO-GEN1TAL SYSTEM. 



globules of the mother cells, but which are set free when the 

 latter are broken. These spermatozoids afterwards show a 

 slight pear-shaped and flattened swelling (head), and a fili- 

 form appendage (or tail), terminating in a fine point (Fig. 

 132). Generally only the mother cells are found in the tubes 

 of the testicle. 



In those animals who enjoy the sexual functions only at 

 certain periods of the year, the testicular secretion occurs 

 only at those periods : they begin in man only at the age of 

 puberty. Spermatozoids are never found in the spermatic 

 fluid before the age of 16 or 17 years. They likewise are 

 liable to disappear in old age. According to Dr. Girault, in 

 man after the age of 55 years the head of the spermatozoids 

 is broader and the tail is shorter; then comes a time when 

 these species of tadpoles (tetards) have almost no tail : the 

 head has absorbed almost the whole of this tail ; a few move- 

 ments may exist, but progression has become impossible : a 

 few scattered ones in whom the tail remains have the power 

 to go forward. 



b. The spermatic fluid is perfected, or in other words, the 

 spermatozoids are set free, only in the epididymis (Fig. 131, 

 E) and in the canals (E', Cd) : they then seem to be ani- 

 mated with very active movements of transportation, but, in 

 reality, only represent the movements of vibratile cilia (see 

 p. 189). Sometimes the head or the neck (union of the head 

 with the tail) of the spermatozoid is encircled by a sort of 

 collar or frill, which is the remains of the nucleus in which 

 the spermatozoid was developed. Their movements become 

 more noticeable in that spermatic fluid which is formed by 

 the product of all the various glands, and as found in the ejacu- 

 latory ducts ; the head moves to and fro by means of the 

 impulsion received from the movements of the tail. No sper- 

 matic fluid is capable of effecting fecundation which has not 

 these vibratile and moving filaments. This sperm, which 

 has a tenacious whitish appearance, and a peculiar odor, con- 

 tains an albuminoid substance called spermatine: this latter 

 substance is not coagulated by heat, contains various salts 

 (alkaline, chlorides, phosphates, sulphates), and, as physical 

 or morphological elements, it also contains a large number 

 of granulations, in addition to the spermatozoids, and likewise 

 certain crystals which are analogous to the ammonio-magnesia 

 crystals of the urine, but now considered to be altered and 

 crystallized albuminates. 



The sperm progresses through the epididymis (Fig. 131, E^ 



