1 92 NORMAL HISTOLOGY. 



that the spermatozoa are formed by the growth in- 

 ward, from the large outer cells, or from cells lying 

 among these, of a long-stemmed bud-like process, 

 whose dilated end divides into a number of longi- 

 tudinal segments, each of which finally becomes a 

 spermatozoon. That the latter is the mode of de- 

 velopment in certain animals, e. g. the rat, would 

 seem to be unquestionable. 



The mature spermatozoa differ in form in different 

 animals ; in man they consist of a flattened, pear- 

 shaped portion, called the head, the small end of 

 which is directed forward ; and a delicate, tapering, 

 almost filiform portion, called the tail; while be- 

 tween the head and tail is a short, narrow segment, 

 called the middle piece. When living, and under 

 favorable conditions, the spermatozoa are capable 

 of performing rapid movements, the whole organism 

 being driven hither and thither by wavy vibrations 

 of the tail. 



TECHNIQUE. 



Spermatozoa. These may be obtained from the sem- 

 inal vessels of man, or from the sediment of urine in 

 which they occur either normally, or under pathological 

 conditions. They are well preserved by a mixture of 

 equal parts of saturated sol. of picric acid, glycerin, and 

 water, in which they may be mounted. 

 - Spermatozoa for comparative study may be readily ob- 

 tained by making an incision into the head of the epi- 

 didymis of a dog, rabbit, or guinea-pig, and receiving the 

 milky fluid which exudes in the above picric acid fluid. 



