70 SCIENCE PROGRESS. 



cells on their course. The inhibitory fibres passing through 

 the nervi erigentes have cells on their course, placed close to 

 the urethra or in the organs themselves. 



Vaso-niotor nerves to these parts. — Stimulation of the 

 lumbar set of fibres causes strong contraction of the arteries 

 to the penis or clitoris, and a slighter contraction of the 

 vessels to the surrounding genital skin and scrotum. The 

 origin of these fibres from the cord is in the main similar 

 to that given above, though in the cat the thirteenth thoracic 

 and first lumbar were also effective. 



The nerve cells on the course of these fibres are placed 

 similarly to those on the other visceral fibres running from 

 the lumbar set. They did not find any satisfactory evidence 

 of the presence of vaso-dilators in these fibres. The 

 lower set of fibres contain many vaso-dilators but no vaso- 

 constrictors. Gaskell ^ found vaso-dilators to the penis in 

 the second and third sacral anterior roots in the rabbit. 

 They were never present in any posterior roots. Sherring- 

 ton '^ obtained the same result in rhesus and in the cat. 

 Francois Franck ^ investigated the vascular nerves to the 

 penis by a plethysmographic method, and recorded at the 

 same time the changes in arterial and venous pressure in 

 the organ. He finds that the mesenteric nerves to the 

 inferior mesenteric ganglia from the sympathetic chain 

 contain many vaso-dilators, and also vaso-constrictors 

 though in fewer numbers. The pelvic nerves contain many 

 vaso-dilators. His experiments were carried out upon 

 dogs which were curarised in order to prevent complica- 

 tions by other muscular influences. 



Internal generative organs. — Our knowledge of the 

 innervation and course of the fibres to the internal generative 

 organs also largely depends upon the researches of Langley 

 and Anderson.* They find that for these pelvic viscera 

 there is only one set of nerves, which come from the 

 lumbar roots. These cause very strong contraction of the 



^ /ourn. of Physiol., vol. viii., 1S87. Proc P. S., p. 4. 

 -Ibid., vol. xiii., p. 686, 1892. 



^ Arch, de Physiol., vol. xxvii., pp. 122 and 138, 1S95. 

 ^ Journ. ofPhys., vol. xix., p. 122, 1895. 



