464 Royal Society. 



by the muscular action of the parts or solution in the fluid, it tra- 

 verses the intestinal canal unchanged, except at the surface, which 

 is then alone exposed to the action of the intestinal fluids. 



16. It is not necessary for the conversion of starch into glucose 

 that the fluids in the duodenum or other parts of the intestinal 

 canal should be alkaline, or even neutral, for in several of the expe- 

 riments the contents of every part of the alimentary canal had an 

 acid reaction. 



17. The greater part of the intestinal mucus is not excremen- 

 titious, for little, if any, mucus is perceptible in the faeces in normal 

 digestion, except at their surface, whereas the greater proportion of 

 the contents of the small intestine consists of mucus. A consider- 

 able quantity of mucus is seen in the caecum, but it rapidly dimi- 

 nishes in the colon, and is scarcely detectible in the fapces, except 

 that on the surface, which is probably derived from the mucous 

 membrane of the rectum. The author raises the question, whether 

 one of the chief functions of the caecum is not to effect the conver- 

 sion of the intestinal mucus into some other substance capable of 

 re-entering the blood, and performing some ulterior purpose in the 

 animal economy. 



18. In normal digestion, the separation of the epithelium of the 

 mucous membrane of the intestine is the exception instead of the rule, 

 as stated by some physiologists. The author questions the theory of 

 the detachment of the epithelium of the villi in each act of absorp- 

 tion, on the grounds that the presence of detached epithelium was 

 unfrequent in the whole course of his experiments ; that epithelium 

 is readily detached by manipulation ; that the continual reproduc- 

 tion of such a vast amount of cell-tissue must necessarily be accom- 

 panied by a vast expenditure of vital force ; and finally, that it is 

 not necessary, because fluids readily penetrate epithelial mem- 

 branes. 



19. The passage of a given food through the whole length of the 

 intestinal canal may occupy a comparatively short time, especially 

 when the animal is fasting. In one experiment, where a pigeon 

 refused food until the faeces contained no visible debris of previous 

 food, starch-granules were detected in the faeces within two hours 

 after a meal, and this although the intestine of this animal is ex- 

 tremely narrow and about a yard in length. 



20. A remarkable circumstance in the digestion of starch or 

 starch foods is the constant presence of myriads of Vibriones in the 

 lower part of the intestinal canal. They are generally first observed 

 in the lower part of the small intestine, as minute brilliant points, 

 just visible with a power of 600 diameters, in active move- 

 ment. They increase in numbers towards the caecum, in which a 

 large number of fully-developed vibriones are constantly seen. 

 These minute organisms increase in size and length in the colon 

 and rectum, and their fissiparous mode of propagation, first described 

 by the author in the ' Quarterly Journal of Microscopical Science,' 

 may be distinctly traced by examining the contents of these por- 

 tions of the intestine. 



