644 SYMPATHETIC AND OTHER SYSTEMS OF NERVES. 



Frangois-Franck and Hallion 1 (1896, 1897) have investigated in the 

 dog the vasomotor supply of the liver, the pancreas, and the small 

 intestine, and the first part of the large intestine. They found that 

 the vasomotor fibres in each case leave the spinal cord by the sixth 

 thoracic to the second lumbar nerve inclusive. The vessels of the 

 large intestine only occasionally receive fibres from the sixth thoracic ; 

 the vessels of the small intestine sometimes receive vasomotor fibres 

 from the fifth, and occasionally from the fourth thoracic. The maximum 

 effect on the intestine appeared to be obtained from the twelfth and 

 thirteenth thoracic nerves. The second lumbar had a slight effect only 

 upon the vessels of the pancreas. 



Lastly, Bunch 2 has experimented on the viscero-motor and viscero- 

 inhibitory action of the spinal nerves on the small intestine of the dog 

 and cat. He finds the innervation to extend from the sixth thoracic to 

 the second, third, fourth, or fifth lumbar. The greatest effect was 

 obtained from the eighth thoracic to the first lumbar. 



The several observations given above do not enable us to form a 

 simple and consistent scheme of the innervation of abdominal viscera, 

 and we may consider the matter from another point of view. 



By dissection, it is easy to see that a large proportion of the 

 splanchnic nerve fibres arise from the white rami communicant es, 

 running in the sympathetic chain for a variable distance. And there 

 is good reason to believe that all the splanchnic fibres are the direct 

 continuation of the fibres of the white rami (cf. p. 646). If this be so, 

 it follows that if any white ramus can be shown not to send fibres to 

 the splanchnic nerves, the spinal nerve from which the white ramus 

 springs, does not send fibres to the solar ganglia. 



In the cat and dog the fibres of the great splanchnic nerve can be 

 traced upwards in the sympathetic chain as far as the sixth thoracic 

 ganglion, 3 and this was one of the facts which led me earlier to place the 

 upper limit of connection of the spinal cord with the solar ganglia at 

 the sixth thoracic nerve. But, on examining the course of the white 

 rami, some fibres of the fifth thoracic ramus can be seen to descend in 

 the sympathetic chain. As these fibres do not run to the vertebral 

 ganglia (cf. p. 634), we may conclude that they run to the splanchnics. 

 It is possible that a few fibres also descend from the fourth white ramus. 

 But, so far as I have seen, none of the fibres of the third white ramus 

 (cat) run downwards. We may then conclude that the uppermost nerve 

 to send fibres to the solar ganglia is the fourth or fifth thoracic. 



The fibres of the lowest splanchnic strand in the cat usually leave 

 the sympathetic chain a little above the third lumbar white ramus. 4 

 There is some variation here, according as the arrangement of nerves 

 is anterior or posterior. On tracing the white rami, it can be seen that 

 the second lumbar white ramus constantly sends fibres to the smallest 

 splanchnic, and that the third lumbar white ramus sends a few fibres to 

 it, if the arrangement of nerves is posterior. Probably, in the dog, the 



1 Arch, de physiol. norm, etpath., Paris, 1896, p. 478 (intestine) ; ibid., 1896, p. 921 

 (liver) ; ibid., 1897, p. 661 (pancreas). These authors stimulated the sympathetic chain 

 or the white rami, and not the spinal nerves in the vertebral canal. 



2 Jon. Physiol., Cambridge and London, 1898, vol. xxii. p. 357. 



3 In man, it is said that the splanchnic fibres can be followed up to the level of the 

 second or third thoracic ganglion. 



4 In man, the smallest splanchnic leaves the sympathetic chain about the level of the 

 twelfth thoracic ganglia. 



