REPRODUCTION. S57 



gen; in salmon it forms nearly a third of the whole weight. By 

 breaking up the protamins by acids it was found that the chief ele- 

 ment in the protamins is arginin, with the hexone bases. In the 

 semen of the carp (cyprinus carpio) Miescher obtained no protamin, 

 but a "peptonelike" substance with basic properties which is a histon, 

 which makes bases very easily with acids. The histon possesses the 

 usual properties of the albumins. 



The nucleo-proteids in the heads of all spermatozoa are a nucleic 

 acid compound. The nucleic acids of sperm are organic phosphoric 

 acid combinations. The protamins and histon have been found only 

 in the semen of some fishes, and not in that of mammals. Burian 

 Asher und Spiro's Ergebnisse der Physiologic, Part I, 1904. 



Erection. The erectile tissue of the male is formed by the 

 penis, formed of corpora cavernosa and the corpus spongiosum. 

 During erection the penis is gorged with blood, due to the arterioles, 

 which are supplied by vasodilator nerves in the nervus erigens. 

 Besides the vasodilation, the return flow of blood by the dorsal vein 

 is partially arrested by the muscle of Houston. The smooth mus- 

 cles of the trabeculae also aid in the act of erection. Erection is a 

 reflex phenomenon, and the center is located in the lumbar cord. The 

 sensory nerve concerned is the pudic, for Eckhard found that section . 

 of this prevented, in the dog, any erection when the glans penis was 

 irritated. Other irritations, as of the testes or the prostatic urethra, 

 lead to erection. A full bladder in the morning is also frequently 

 accompanied by a passive erection, due to a compression of the ven- 

 ous plexus of Santorini by the bladder. The genito-spinal center 

 in the lumbar region is also affected by impulses coming from the 

 brain, which may be of two kinds, excitatory and inhibitory. The 

 penis also receives vasoconstrictor fibers, which emanate from the 

 second to fifth lumbar nerves, and reach the penis either by the 

 pudic or the hypogastric plexus. The surface of the organ, its 

 integument, usually slightly folded, becomes tense, and the engorged 

 subcutaneous veins are seen beneath the surface. During erection 

 the clonic contraction of the bulbo-cavernous muscle pushes the 

 blood towards the glans. These muscles are aided in a similar man- 

 ner by the ischio-cavernous muscles. These two muscles have been 

 compared to peripheral hearts in the vascular movement of this 

 organ. In disease of the spinal cord erection is often lost or sup- 

 pressed, so that coitus is impossible. 



EJACULATION OF SEMEN. At the moment of erection the 

 urethral canal becomes filled with a secretion of its different glands. 



