258 OF THE FUNCTION 



the abdomen downwards, overcoming the resistance 

 of the os coccygis and of both sphincters, the inner 

 of which is a remarkable bundle of circular fibres, 

 the outer, a truly cutaneous muscle. After the excre- 

 tion, the effort of the abdomen having ceased, the le- 

 vator ani chiefly retracts the intestine, which is again 

 closed by its sphincter.* 



NOTES. 



(A) Pechlin's experiment was simply to include a portion of 

 intestine between two ligatures, so that the fluid secreted into 

 the canal might be collected. 



(B) A great part of the chyle is generally formed and absorbed 

 before the digested mass reaches the ileum.f On arriving in the 

 large intestines, the mass undergoes fresh changes, at present 

 unexplained, and is converted into excrement. Here it is that 

 the true succus entericus must be poured forth. 



The gas of the stomach contains, besides azote and carbonic 

 acid gas, oxygen, and very little hydrogen ; while that of the 

 small intestines contains, besides the two former gases, no oxygen 

 and abundance of hydrogen : that of the large intestines has 

 less hydrogen and carbonic acid, and likewise no oxygen. Little 

 or no gas is found in the stomach during chymification. 



The following are the results of M. M. Majendie's and Chev- 

 reuil's analysis of the gases of the alimentary canal. 

 In the stomach of a man just executed, 



* All these parts may be seen as they exist in each sex, in Santorini's 

 Fosth. Tables, xvi. and xvii. 



f Dr. Front, Thomson's Annals of Philosophy. 1819. 



