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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    with the central nervous system by way of the vagus nerve, while the corresponding cells and nerves for the cloacal region are con¬ nected with the central nervous system by way of the pelvic nerve (Fig. 5). The small intestine is usually described as separated from the large by a valve, the ileo-coecal valve ; but, as Elliott has shown, there is in reality no valve here but a strong sphincter muscle, the ileo-colic sphincter, which terminates the intestine proper. The hind gut originally formed a tube composed of three chambers, to which Gadow gave the names Coprodoeum, Uro- doeum, and Proctodceum. The coprodceum was separated from the urodceum by a sphincter, and the urodoeum from the proc- todoeum by another sphincter; thus relaxation of the urinary sphincter allowed the urine collected in the urodoeum alone to pass out, while relaxation of the internal sphincter of the rectum as well as of the ordinary sphincter allowed the faeces to pass out (Fig. 7). The coprodoeum has in the higher vertebrates separated entirely from the urodoeum and opens directly to the exterior, still retaining its sphincter muscle, the internal sphincter of the anus. The urodoeum or bladder opens to the exterior by way of the urethra and still retains its original sphincter muscle in the shape of the urethral muscles and the unstriped sphincter muscle. Thus there are the following sphincter muscles which termin¬ ate the different regions of the gut:— 1. The ileo-colic sphincter at the end of the small intestine. 2. The internal anal sphincter at the end of the coprodoeum. 3. The internal vesical sphincter and the urethral muscles at the end of the urodoeum. The motor nerve supply to all these muscles is arranged on a uniform plan (Fig. 7). Thus Elliott has shown that the ileo-colic sphincter contracts upon stimulation of the superior splanchnic nerves, and that its motor nerve cells are situated in the superior mesenteric ganglion. Langley and Anderson have shown that the internal anal sphincter contracts on stimulation of the inferior splanchnics and its motor nerve cells are situated in the inferior mesenteric ganglion. Finally Elliott has shown that the internal vesical sphincter and the muscles of the urethra con¬ tract on stimulation of the inferior splanchnics, and their motor nerve cells are situated in the inferior mesenteric ganglion. The motor fibres of these sphincter muscles thus arise from
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