ITS FORMATION. 89 



and fails with those extractive bodies which are only soluble in 

 alcohol a fact which plainly indicates that these substances are 

 not of a biliary nature. 



The positive experiments, made under different physiological 

 relations, by Bidder and C. Schmidt, on the biliary secretions of 

 animals, appear, at first sight, to refute this hypothesis. These 

 careful observers found that fat animals yield considerably less 

 bile than lean ones, and that, when they were fed on fat (bacon, 

 suet), the quantity was smaller than in the case of animals fed on 

 substances containing the smallest possible portion of fat. These 

 differences were no longer appreciable in animals which had been 

 kept for some time without food. The fact that fat animals yield 

 less bile than lean ones, is in harmony with an observation already 

 referred to, that the metamorphosis of matter is usually accom- 

 plished more slowly, and in a smaller degree, in organisms disposed 

 to secrete fat in abundance ; we need only mention that fat animals 

 expire less carbonic acid in equal periods of time than lean but 

 strong ones. The inference to be drawn from these observations 

 is, not that fat animals and fat persons yield little bile because they 

 are fat, but rather that such animals and persons have grown fat in 

 consequence of their secreting little bile. 



It can scarcely excite surprise that animals which are fed exclu- 

 sively on fat should secrete less bile ; for all fat is not applied to 

 the formation of bile, neither is it fat alone which is employed for 

 that purpose ; for we shall presently see that fat constitutes only a 

 part of the material necessary for the formation of bile. Daily 

 experience, derived from the pathological observation of cases of 

 fatty liver, shows us also that an excess of fat is prejudicial to the 

 secretion of bile, for, although the hepatic cells are often dilated 

 to twice the normal size in these cases, the quantity of bile is very 

 much below the normal standard. 



Lastly, the circumstance that animals which are fasting secrete 

 more bile than those which are fed exclusively on fat, does not 

 refute this hypothesis ; for, as much sugar arrests the progress of 

 vinous fermentation, much fat also impedes the formation of bile in 

 the hepatic cells. As far as we are able to observe the metamor- 

 phosis of tissue in animals which have been kept for a long time 

 without food, it would seem that this change is not limited to 

 those histological elements which contain nitrogen, for we find that 

 the fat rapidly disappears during inanition. We have already 

 spoken, in the first volume, of the possibility of the formation of 

 fat from the protein-bodies. If the observations of the above- 



