DIGESTION. 60S 



There are strong reasons for believing that bile is not the only 

 substance formed in the liver. It has been long known that, 

 when the liver is diseased, the quantity of urea in the urine is 

 greatly diminished. Hence it is not unlikely that urea, and 

 perhaps even uric acid are formed in that organ. Liebig has re- 

 marked that 5 atoms protein, 15 atoms starch, 12 atoms water, 

 and 5 atoms oxygen, may be resolved into 9 atoms choleic acid, 

 9 atoms urea, 3 atoms ammonia, and 60 atoms of carbonic acid. 

 Thus, 



Atoms. Atoms. 



5 protein, =C 40 Hi 80 Az30 7 ^ ( 9 choleic acid, =C 3 H 197 Az 9 O" 



15starch, =C 180 H 150 O 150 I = J 9 urea, . =C* 8 H 36 Az' 8 O 18 



12 water, = H' 2 CM 2 ] 3 ammonia, = H 9 Az 3 



5 oxygen, = O 5 J 1 60 carbonic acid, =C 60 O>* 



But this does not throw much light upon the subject, as we have 

 no evidence that starch, or any thing resembling it in composi- 

 tion, exists in the blood, from which the bile and urea are se- 

 creted. 



Liebig affirms that none of the bile is excreted with the faeces. 

 He conceives that it is all taken again into the system, and con- 

 verted into carbonic acid and water during its circulation through 

 the body, for the purpose of producing animal heat. The opi- 

 nion is bold and ingenious. But its accuracy seems to me to 

 be belied by the phenomena. The colour of the faeces indicates 

 the presence of choleic acid, which may have lost its solubility 

 in alcohol, in consequence of having entered into combination 

 with the excrementitious matter. Were the bile absorbed into 

 the system, it ought to be present in the blood, which is never 

 the case except in the disease called jaundice. 



The chyle formed in the lower part of the duodenum and in 

 the other small intestines is taken up by the open mouths of the 

 lacteals, and conveyed by them to the thoracic duct. From the 

 difficulty, or almost the impossibility, of obtaining a sufficient 

 quarttity of chyle in a state of purity, it has hitherto been but 

 imperfectly examined by chemists. Indeed, as in the thoracic 

 duct, it is always mixed with lymph, a liquid exhaled in order to 

 moisten and lubricate all the shut cavities of the body, from 

 which it is taken up by the lymphatics, and conveyed to the tho- 

 racic duct, it is impossible to procure it in a state of purity except 

 in the lacteals. Hence the quantity of pure chyle procurable 

 can never exceed a few drops. The facts hitherto ascertained 



