22O 



NORMAL HISTOLOGY. 



FIG. 263. 



inner envelope of involuntary muscle. From the latter muscu- 

 lar septa penetrate in all directions between the acini of glandular 

 tissue ; immediately surrounding the urethra a thick muscular layer 



also exists. 



The prostatic acini may be regarded as highly developed ure- 

 thral glands, which they closely resemble, opening by a dozen or 



more ducts on the free sur- 

 face of the urethra. Of 

 these ducts two of especial 

 size empty on either side 

 of the urethral crest, and, 

 repeatedly subdividing, 

 communicate with the 

 numerous closely - packed 

 acini constituting the cen- 

 tral lobe. The other di- 

 visions of the gland are 

 simpler in structure, since 

 they contain tubular al- 

 veoli, much less closely 

 placed, which open into a 

 slightly wavy duct. 



The epithelium lining 

 the alveoli is short colum- 

 nar in character, and fre- 

 quently possesses more 

 than a single row of cells, 

 smaller spherical or pyri- 

 form elements filling up 

 the interstices between the 

 outer ends of the somewhat tapering cells next the lumen. The 

 nuclei of the epithelial elements are situated eccentrically, lying 

 nearer the ends of the cells directed towards the basement-mem- 

 brane. These cells in elderly subjects not infrequently contain 

 pigment. 



In addition to the fibrous and elastic connective tissue among the 

 acini of the gland, bundles of involuntary muscle pass in all di- 

 rections between the alveoli, and in many places constitute almost 

 the entire tissue separating the adjacent acini. While present in all 

 parts of the gland, the quantity of muscle varies in different parts of 

 the organ ; it is poorest in the central lobe, where the acini are best 

 developed, and richest in the upper part of the posterior post-ure- 

 thral division and in the extreme fore part of the organ. In the low- 

 est part of the posterior segment the involuntary muscle is supple- 



Section of human prostate, exhibiting general disposition 

 of acini : a, fibrous envelope ; t, groups of tubular acini ; 

 c, sections of prostatic ducts ; e, interacinous fibro-mus- 

 cular tissue. 



