CHAPTER IV 



MECHANICS AND CHEMISTRY OF DIGESTION IN THE INTESTINE 



CONTENTS. 1. Artificial digestion with the three intestinal secretions : 

 pancreatic juice, bile, succus entericus. 2. Mechanism of bile -excretion in the 

 intestine, and innervation of muscles of common bile-duct. 3. Natural digestion 

 of chyme in small intestine. 4. Putrefactive processes in the intestine. 5. Effects 

 of extensive resection of small intestine in animals and man. 6. Peristaltic move- 

 ments of intestine. 7. Central and peripheral innervation. 8. Post-mortem auto- 

 digestion. Why it does not occur during life. Bibliography. 



THE last chapter proves, as already stated, that the digestion 

 of food-stuffs in the mouth and stomach is very imperfect. 

 Contrary to earlier opinions, the acid pulp, known by the name 

 of Chyme, does not differ, chemically speaking, in its essentials from 

 the mass of the food-stuffs ingested, whether these be raw or 

 modified by cooking. The changes which the foods undergo in 

 the mouth are principally mechanical ; those which they undergo 

 in the stomach are principally antiseptic. But if not absolutely 

 indispensable to life, both these changes serve to prepare for and 

 to facilitate the true and complete digestion that takes place in 

 the small intestine, which is the subject of this chapter. 



I. The acid chyme, after passing into the duodenum, en- 

 counters three alkaline secretions pancreatic juice and Hie in 

 the duodenum, succus entericus throughout the small intestine by 

 which it is gradually neutralised. It is only in the last part of 

 the small intestine that the intestinal contents give an alkaline or 

 neutral reaction. The cause of the acidity of the intestinal contents 

 has been studied by many authors (Nencki and Zaleski, Moore and 

 Rockwood, Hemmeter, Gillespie, C. Foa, U. Lombroso, etc.). 



According to most authorities the acid reaction of the intestinal 

 contents is due to a complex of factors, e.g. acidity of the gastric 

 juice, the fatty acids liberated from alimentary fats, the lactic acid 

 developed during digestion of the carbohydrates, the carbonic acid 

 formed by the action of stronger acids on the carbonates, etc. 



C. Foa (1906), who undertook to control and confirm the 

 observations of various authors in regard to the actual and potential 

 reactions of the digestive secretions (which all present an almost 

 neutral actual reaction, the gastric juice alone giving a strongly 



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