The involuntary nervous system / by Walter Holbrook Gaskell.

  • W. H. Gaskell
Date:
1920
Catalogue details

Licence: In copyright

Credit: The involuntary nervous system / by Walter Holbrook Gaskell. Source: Wellcome Collection.

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    on stimulation of the splanchnic nerve. I have already discussed the share taken by the sympathetic system in the innervation of the small intestine but have not considered the stomach and oesophagus. As far as concerns the oesophagus and its termina¬ tion in the cardiac sphincter of the stomach, there is no evidence that sympathetic motor fibres reach to this region ; the motor supply is entirely from motor cells connected with the vagus nerve. The passage of food from the stomach to the intestine is regulated by a sphincter muscle at the pylorus, and there is some evidence to show that a musculature exists here which is inner¬ vated after the same fashion as the rest of the sphincter group of muscles already considered. Elliott has given evidence of some contraction of this sphincter muscle in the rabbit upon stimula¬ tion of the splanchnic nerve, and he finds in the bird a contraction of the whole of the duodenal region upon stimulation of the same nerve. Still more extensive is this musculature in the frog, ac¬ cording to the evidence of Dixon, who states that the muscula¬ ture of the whole stomach of that animal contracts either upon stimulation of the splanchnic or in consequence of the direct action of adrenaline. There are then indications in this region of a musculature supplied with sympathetic motor fibres which varies in its extent in different animals, just as according to Elliott (see p. 57) the corresponding sphincter musculature of the bladder varies greatly. Undoubtedly, as in the small in¬ testine, the musculature of the main body of the stomach in all mammalia is supplied with motor fibres from cells connected with the vagus nerve. Where then are the motor cells to this intestinal unstriped musculature, to which the vagus fibres are the connector nerves ? In such a very low vertebrate as the lamprey the fibres of the vagus nerve can be traced in the walls of the intestine and, scattered along the nerve fibres, nerve cells can be seen with which they are in connexion. These scattered nerve cells in¬ clude among them the motor cells to the intestinal muscle and are situated in the walls of the intestine itself. In the higher forms of vertebrates these nerve cells form a characteristic layer between the circular and longitudinal muscles of the intestine and, with the nerve fibres in connexion with them, are known by the name of Auerbach’s plexus. The cells of Auerbach’s plexus must in my opinion be regarded as the motor nerve cells, from
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