212 STUDENTS HISTOLOGY 



the central part of the tube, in various stages of formation. 

 The tails of the spermatozoa point toward the center of the 

 tube, and the heads are directed toward the epithelial lining. 

 Among the epithelial cells some may be found that are under- 

 going karyokinesis. 



Careful study of selected specimens has shown that the epithe- 

 lial cells next the basement membrane are of two sorts : (1) The 

 sustentacular cells. (2) The spermatogenic cells. The sperma- 

 tozoa are derived from the spermatogenic cells. 



Spermatozoa may be obtained from the fresh testicle or epidi- 

 dymis of some one of the domestic animals. The human sperma- 

 tozoon is about 50 /* in length. It consists of a short oval head, a 

 short middle piece or body, and a long tail. The tail possesses 

 active vibratile movements. 



THE P-ROSTATE GLAND. 



The prostate gland consists of a number of tubular acini, which 

 are imbedded in a muscular and fibrous framework. The muscle 

 is of the unstriated variety, and is very abundant. The tubular 

 glands are lined by columnar epithelium. They open by a num- 

 ber of ducts into the urethra. Certain small, round, concentrically 

 laminated bodies, the prostatic concretions, often occur in the ducts 

 and acini, especially in old subjects. The secretion of the prostate 

 gland is thin and nearly transparent, containing granules and 

 epithelial cells. 



ERECTILE TISSUE 



Erectile tissue is best demonstrated in the penis, preferably of a human 

 infant, cut in transverse section. The two corpora cavernosa and the corpus 

 spongiosum are readily distinguished. The erectile tissue can be studied in 

 the corpora cavernosa. 



The connective tissue surrounding the cavernous bodies gives 

 off numerous trabeculse, forming a framework, enclosing spaces. 

 These spaces are lined by endothelium, and communicate with one 

 another freely. The arteries open into them, and the veins open 

 from them. During erection they become greatly distended with 

 blood. Similar erectile tissue occurs in the external generative 

 organs of the female. 



