646 SYMPATHETIC AND OTHER SYSTEMS OF NERVES. 



The inferior mesenteric ganglion gives off several strands — the 

 colonic nerves — which accompany the inferior mesenteric artery. They 

 give off also, on each side, a hypogastric nerve which runs downwards to 

 the pelvic plexus, and ascending branches which run partly to the de- 

 scending colon and partly to the solar plexus. 



Stimulation of the colonic branches causes great pallor, with inhibi- 

 tion and sometimes contraction of the descending colon and rectum ; and, 

 in the cat and dog, slight contraction and pallor of the internal anal 

 sphincter. 



The ascending branches have a similar but smaller effect upon the 

 upper part of the descending colon. 



The hypogastric nerves cause great pallor with more or less contrac- 

 tion of the Fallopian tubes and uterus, or corresponding organs in the 

 male ; weak contraction of the bladder, chiefly in the region around the 

 ureters, but little or no contraction of the blood vessels ; pallor with 

 inhibition or contraction of the rectum and end of the descending colon ; 

 slight contraction and pallor of the internal anal sphincter with its 

 mucous membrane, and of the external generative organs. 



The inferior mesenteric ganglia in the cat receive nerve fibres from 

 the first to the fourth lumbar nerves, and, when the arrangement of 

 nerves is posterior, from the fifth lumbar nerve also ; occasionally they 

 receive a few fibres from the lower thoracic nerves. In the dog the 

 origin of the fibres is a little higher, and in the rabbit it is a little lower, 

 than in the cat. 



Taking the matter generally, it may be said that each spinal nerve 

 which sends fibres to the inferior mesenteric ganglion, is capable of pro- 

 ducing all the effects which we have mentioned above as produced by 

 stimulating the nerves given off by the ganglia. 



The intensity of the effects with an anterior arrangement of nerves 

 is marked with the third or fourth lumbar, moderate or slight with the 

 second lumbar, and slight or absent with the first lumbar. 



With a posterior arrangement of nerves the fifth lumbar also pro- 

 duces an effect, the effect becoming greater as that of the third lumbar 

 diminishes. 1 



Nerve-cell connection of the sympathetic fibres supplying the 

 abdominal viscera. — It can easily be shown in the rabbit that the very 

 great majority of the fibres running from the spinal cord to the abdo- 

 minal viscera end in the pre-vertebral ganglia. After injection of a 

 small amount of nicotin in the rabbit, the nerve roots, the splanchnics 

 proper, 2 and the inferior splanchnics 3 have either no effect or a mere 

 trace on the blood vessels or abdominal and pelvic viscera ; but all the 

 normal effects can be readily obtained by stimulating the fibres given 

 off by the pre-vertebral ganglia. And on degeneration of the anterior 

 roots of a nerve sending fibres to a splanchnic strand, numerous 



1 For the differences in the innervation of the several organs which occur in corre- 

 spondence with the arrangement of the spinal nerves, for the slight differences which exist 

 in the innervation of the several organs, and for an account of the literature of the 

 subject, see Langley and Anderson, Journ. Physiol., Cambridge and London, 1895, vol. 

 xviii. p. 67 (lower part of intestine) ; ibid., 1895, vol. xix. p. 71 (bladder) ; p. 86 (external 

 generative organs) ; p. 122 (internal generative organs). 



2 Langley and Dickinson, Proc. Boy. Soc. London, 1889, vol. xlvi. p. 424 ; Langley 

 Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 223 ; Bunch (ibid., 1897, vol. 

 xxii. p. 357) comes to the same result as regards the motor and inhibitory fibres of the 

 small intestine. 



3 Langley and Anderson, ibid., 1895, vol. xix. p. 131. 



