04 INTRODUCTION. 



melted at the temperature of the body, and floats in the form 

 of oil on the alimentary mass. It passes then into the small 

 intestines unchanged, is emulsified by the pancreatic juice, 

 and absorbed by the lacteals. A small quantity of fat is 

 absorbed by the radicles of the portal vein. After a full 

 meal, the blood of a carnivorous animal frequently contains 

 enough fatty emulsion to form a thick white pelicle on cooling. 



The question as to the possibility of the formation of fat 

 in the organism may be now considered as definitely settled. 

 It has been shown by Liebig, Boussingault, and others, that 

 in young animals especially, the fat in the body cannot all be 

 accounted for by that which has been taken in as food added 

 to that which the body contained at birth. The experiments 

 of Boussingault, 1 on this point, on young pigs, are very con- 

 clusive, and demonstrate that fat must be produced some- 

 where in the organism. Bernard a has shown that an emul- 

 sive substance, which he regards as fat in combination with 

 organic nitrogenized matters, is produced by the liver, and 

 is taken up by the blood of the hepatic vein. He believes 

 that it is produced at the expense of the amylaceous or sac- 

 charine elements of food. 



It is very certain that the generation or deposition of 

 fat in the body may be influenced very considerably by 

 diet, and the conditions of the system. This is daily exem- 

 plified in the inferior animals, and is true, though it is not 

 perhaps as universal, in the human subject. It has been 

 found that a diet consisting largely of fatty, amylaceous, and 

 saccharine principles favors the accumulation of fat, while 

 an exclusively nitrogenized diet is unfavorable to it, and will 

 produce emaciation, if rigidly followed. Muscular activity. 

 it is well known, is unfavorable to the accumulation of fat ; 

 which may account in a measure for its greater relative quan- 

 tity in the female. In some individuals, especially when its ac- 



1 BOUSSINGAULT, Chimie Agricole, Paris, 1854. 



8 BERNARD, Lefons de Physiologie Experimentale, Paris, 1855, p. 154 et seq. 



