490 



HISTOLOGY 



FIG. 459. Callus domesticus ; upper part 

 of oviduct. Shows a simple, tall, colum- 

 nar epithelium. X noo. 



The study of organs of copulation 

 is principally a morphological one. 

 The histology of these structures is 

 very generally that of mere integu- 

 ment muscle and other general tis- 

 sues. 



We shall examine one case of a 

 tissue specifically designed to aid 

 this process in the mammals, the 

 erectile tissue. The urethral portion 

 of the human corpus cavernosum will 

 represent the tissue which is used 

 to enlarge and make rigid the intromittent organ (Fig. 461). 



The tissue consists of a con- 

 nective tissue containing many 

 smooth muscle cells. It is en- 

 tered by arteries whose walls 

 show peculiar elastic tissue 

 enlargements directly under the 

 intima. These arteries end, in 

 the cavernous tissue, in capil- 

 laries which in turn discharge 

 their contents into a series 

 of thin-walled veins which 

 are so large and so numerous that they give the tissue its name, 





FIG. 460. Callus domesticus; lower region of ovi- 

 duct with short tubular glands. X 1 100. 



ynus. /. 



FIG. 461 . Small area from a sec- 

 tion through the corpus caverno- 

 sum of an infant, v., vein; art., 

 artery; mus.f., smooth muscle 

 fibers. X 500. 



the cavernous tissue. 



These cavernous veins are filled with 

 blood, and the efferent veins are so com- 

 pressed at the same time that this blood 

 cannot escape. This produces the neces- 

 "V, sary rigidity of the tissue. 



Technic. The different nidamental 

 tissues require a variety of treatment. 

 Many of them must be sectioned serially 

 to work out the small and complicated 

 passages, glands, etc. The combined cel- 

 loidin and paraffin method is most useful 

 here, especially when the tissue is stained 

 in bulk. In order to insure a series un- 

 broken by stiff and curling sections, it is 

 best to use .a very weak celloidin mixture. 



Many of the nidamental structures will 

 be found lying in the passages and will 



