334 VETERINARY PHYSIOLOGY 



ordinated contraction and relaxation, which together con- 

 stitute a true j^eristalsis. 



But, Avhile peristalsis is thus independent of the central 

 nervous system, it is nevertheless controlled by it. The 

 splanchnic nerves inhibit, while the vagus, to the small 

 intestine and possibly the first part of the large gut, and 

 the nervi erigentes or pelvic nerves to the greater part 

 of the large gut are augmentor nerves, increasing the 

 peristalsis. Stimulation of the splanchnic fibres, which 

 inhibit peristalsis, causes contraction of the ileo-Ciecal 

 sphincter. 



The movements of the intestine may be inhibited either 

 by interference with the local nervous mechanism or by 

 reflex action through the central nervous svstem. Thus, it 

 has been found that roughly handling the gut will lead to a 

 prolonged inhibition, even after the extrinsic nerves have 

 been cut. Other stimuli — such as crushing the testis under 

 an anaesthetic — lead to a reflex inhibition, which is manifest 

 only if the splanchnic nerves are intact. When a cat, 

 under observation with X-rays, manifests signs of anger, the 

 gastric movements and movements of the small intestine 

 are checked. Under these conditions the movements 

 of the large intestine mav be increased and the faeces voided. 



The Ileo-Caecal Sphincter and Valve. — -This sphincter pre- 

 vents the free passage of the contents of the small into the 

 large intestine, and causes a stasis in the ileum — possibly to 

 allow of complete absorption of all the nutrient constituents. 

 It relaxes from time to time, and allows the contents to be 

 forced into the large gut. The valve is formed by a sleeve- 

 like projection of the end of the ileum into the ct^cum, but 

 it does not completely prevent the backward passage of the 

 contents of the large into the small intestine. 



Usually the contents of the small intestine travel down 

 at about lb meti-es per hour. In abnormal conditions the 

 rate of passage may be greatly retarded or accelerated, 



2. The Large Intestine. 

 In the large intestine peristaltic waves like those of the 

 small intestine are not prominent, and the segmental move- 



