THE MALE REPRODUCTIVE ORGANS. 863 



alkali, and they are precipitated by most of the general precipitants 

 of proteids, such as the neutral salts, the alkaloidal reagents, etc. 

 Their solutions, however, are not coagulated by heat. The molec- 

 ular formula for salmin is given as C 30 H 57 N 17 O 6 . When decom- 

 posed by the action of acids they yield simpler basic products, 

 the so-called hexon bases or diamido-acids, and particularly the 

 base arginin (C 6 H 14 N 4 O 2 ), which is contained in the protamin of 

 the spermatozoa in greater abundance than in any other proteid. 

 The protamins differ from most other proteid compounds by their 

 relative simplicity; they contain no cystin grouping, therefore no 

 sulphur; no carbohydrate grouping in most of the compounds- 

 examined; and no ty rosin complex. In the spermatozoa of some 

 fishes the protamins are replaced by more complex compounds 

 belonging to the group of histons which show properties somewhat 

 intermediate between those of protamins and ordinary proteids. 

 It should be added that these albuminous bases, protamins, have 

 been obtained so far only from the spermatozoa of the fishes and 

 some of the invertebrates. Efforts to obtain similar compounds 

 from the sperm of mammals have been so far unsuccessful. The 

 nucleic acid component of the spermatozoon resembles the same 

 substance as obtained from the nuclei of other cells. In the 

 spermatozoa of the salmon this nucleic acid has the formula C 40 H 56 - 

 N 14 P 4 O 26 . On decomposition by hydrolysis it yields at first some 

 of the purin bases (adenin, guanin), and on deeper cleavage a 

 number of compounds including the pyrimidin derivatives, thymin, 

 uracil, and cytosin. 



The Act of Erection. In the sexual life of the male the act of 

 erection of the penis during coitus offers a most striking physical 

 phenomenon. During this act the penis becomes hard and erect, 

 owing to an engorgement with blood. The structure of the corpora 

 cavernosa and corpus spongiosum is adapted to this function, being 

 composed of relatively large spaces inclosed in trabeculae of connec- 

 tive and plain muscle tissue, the so-called erectile tissue. Many 

 theories have been proposed to explain the mechanism of erection, 

 but it is generally agreed that the work of Eckhard * demonstrated 

 the essential facts in the process. This investigator discovered that 

 in the dog stimulation of the nervi erigentes causes erection. These 

 nerves are composed of autonomic fibers arising from the sacral por- 

 tion of the spinal cord (see Figs. 104 and 105). They arise from the 

 sacral spinal nerves, first to third (dog), on each side and help to 

 form the pelvic plexus. They contain vasodilator fibers to the penis, 

 as well as to the rectum and anus, and also visceromotor fibers to the 

 descending colon, rectum, and anus. Eckhard, Love"n, and others 



* Eckhard, " Beitrage zur Anatomic und Physiologie," 3, 123, 1863, and 

 4, 69, 1869. 



