212 A MANUAL OF VETERINARY PHYSIOLOGY 



ferment, but a chemical substance found in the walls of the small 

 intestines ; this when taken into the blood possesses the singular 

 property of causing the secretion of pancreatic juice. 



Enterokinase, erepsin, and secretin will be dealt with in 

 considering the pancreas. 



Intestinal Digestion in the Horse. 



The contents of the stomach are neutralised by the pancreatic 

 and biliary secretions immediately or shortly after they leave the 

 stomach. So much is this the case that on the duodenal side of 

 the pylorus the reaction of previously acid chyme is neutral, and 

 a few inches along the duodenum it is alkaline ; this alkaline 

 reaction is at first faint, but becomes more marked as the ileum is 

 approached. Ellenberger describes the contents of the small 

 intestines as being acid in the first two-thirds of their length, 

 then neutral as far as the ileum, where they become alkaline ; we 

 have only once found them otherwise than alkaline throughout. 

 He further states that in the fasting horse the contents are alka- 

 line, but that in the digesting animal, whether horse, ox, or sheep, 

 they are acid, the acidity decreasing after passing the common 

 duct, and becoming decidedly alkaline at the posterior portion 

 of the small intestine. This, as we have said, does not agree with 

 the writer's experience in the horse ; it is usual to find the contents 

 of the duodenum next the pylorus neutral, and from this point 

 the bowel is faintly alkaline, the reaction increasing in intensity 

 up to the ileum, where the contents are always markedly alkaline. 

 We have only once found the small bowels acid in the horse, 

 no matter what diet has been given, or at what period of digestion 

 the examination has been made ; a neutral or faintly alkaline 

 reaction in the anterior part of their course, and marked alka- 

 linity in the posterior portion, is doubtless the rule rather than 

 the exception. 



The arrangement of the small intestines suspended or dangling 

 in festoons from the spine through the medium of a very delicate 

 membrane is a construction the advantages of which are not very 

 apparent. It appears to invite trouble. The long mesentery 

 is considered to favour volvulus, but no doubt the chief cause of 

 this latter trouble is tympany. If the bowels be artificially 

 distended with air, loops of them behave in such a way as would 

 lead to twist in the living animal. 



Physical Characters of the Chyme. — The chyme having passed 

 into the bowel, its appearance at once changes, for the acid 

 albumin is precipitated by the alkaline secretion found there. 

 It is now observed that the material consists of clots floating or 

 suspended in a yellowish fluid, extremely slimy in nature, and 



