HEREDITY 163 



The chief anatomical facts respecting the nervous 

 supply of the reproductive organs is given below.* 



* After section of the spinal cord above the lumbar enlarge- 

 ment in dogs, all the processes of generation, including parturi- 

 tion, may stiU take place, which shows clearly that the nervous 

 mechanism of these acts was still complete after the operation. 

 It is, indeed, in the lumbar portion of the spinal cord that the 

 special centres of the various acts included in generation have 

 been located (Ferrier, loc. cit., p. 18). Stimulation of the second 

 and third lumbar nerves in the monkey causes a powerful contrac- 

 tion of the vas deferens (Foster, loc. cit, p. 1510). In the dog and 

 cat fibres passing from the anterior roots of the first and second, 

 and sometimes from the third sacral nerves control the vaso- 

 motor mechanism of the sexual organs. In the monkey they 

 proceed from the seventh lumbar and first sacral nerves {ibid., 

 p. 1509). The nerves of the penis are derived from the pudic 

 nerve, which arises in turn from the third and fourth, and some- 

 times from the second, sacral nerves, and from the hypogastric 

 plexus. The cremaster muscle is supplied by the ilio-inguinal, a 

 branch of the lumbar plexus. The nerves to the testis proceed 

 from the sympathetic system, and are derived from the spermatic 

 plexus, ' a set of delicate nervous filaments which descend upon 

 the spermatic artery from the aortic plexus.' This latter is 

 joined by branches of the lumbar ganglia of the cord. Some 

 fibres reach the testis from the hypogastric plexus, which also 

 supplies the vesiculas seminales. The nerves of the vagina come 

 from the hypogastric plexus of the sympathetic, the fourth sacral, 

 and the pudic nerves ; those of the uterus from the hypogastric 

 and spermatic plexuses, and from the third and fourth sacral 

 nerves. The nerves of the ovaries are derived from the ovarian 

 plexus and from the uterine nerves. 



Thus the nervous supply to the reproductive organs is a very 

 complicated nature, and the only links of importance which can 

 be established at present between them and the centre in the 

 lumbar portion of the cord on which they depend appear to 

 consist of those fibres of the sympathetic system connecting, on 

 the one hand, the spermatic and ovarian plexuses, and on the 

 other hand the hypogasteic plexus with the aortic plexus. It 



11—2 



