G02 FUNCTIONS OF ANIMALS. 



in converting it into chyle. But, as the liquid of the duodenum 

 has never been collected nor examined in a state of purity, little 

 is known respecting its nature. 



Leuret and Lassaigne made a hungry dog swallow small pieces 

 of sponge wrapt up in fine linen. The animal was killed twenty- 

 four hours after. Some of the sponges were found in the sto- 

 mach, and some in the duodenum. The sponges in the stomach 

 contained a mucous, whitish acid liquid ; those in the duodenum 

 a liquid which was yellowish, but little viscid, and but weakly 

 acid. A quantity of this last liquid was mixed with crumb-of- 

 bread in a phial, and kept for some hours in a temperature of 88. 

 In eight hours the bread disappeared, and there remained a thick 

 homogeneous yellowish liquid, in which iodine detected the pre- 

 sence of a little starch.* But we have no evidence that the li- 

 quor thus examined was secreted by the duodenum. Undoubt- 

 edly the sponges would remain for some time, and would imbibe 

 liquid in the stomach. 



There are two liquids which are poured into the duodenum, 

 and which are generally considered as intimately connected with 

 the conversion of the chyme into chyle. These are the pancrea- 

 tic juice and the bile. An account of both of these liquids, so 

 far as they have been investigated, has been given in a preceding 

 part of this work. 



The pancreatic juice is not abundant. It was long considered 

 as similar to saliva; but later investigations have shown that 

 its nature is different. It is weakly acid, and contains pancreatin 

 and casein ; but the function of these substances in the process 

 of digestion or of the conversion of the chyme into chyle is not 

 yet understood. 



Bile consists essentially of choleate of soda. One use of the 

 soda may be to neutralize the acid contained in the chyme. 

 But the steps by which the chyme is converted into chyle and 

 excrementitious matter are not yet understood. Doubtless the 

 liquids secreted in the duodenum and small intestines perform 

 the most important part of this extraordinary change. The cho- 

 leic acid probably unites with the excrementitious matter, increas- 

 es its consistence, and, by its stimulating qualities, induces the in- 

 testines to propel it onwards, in order to its expulsion from the 

 body. 



* Recherchcs sur la Digestion, p. 144. 

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