ORIGIN OF FATS. 445 



say olein, but a very slightly increased percentage of that 

 particular fatty substance is found in its adipose tissue, 

 which goes to show that if fats come from fats eaten, these 

 latter are first pulled to bits by the living cells and built up 

 again into the forms normal to the animal; so that, even with 

 fatty food, the fats stored up seem to be in most part 

 manufactured in the Body. 



In still another way it is proved that fats can be constructed 

 in the Body. In animals fed for slaughter, the total fat 

 stored up in them during the process is greatly in excess 

 of that taken with their food during the same time. For ex- 

 ample, a fattening pig may store up nearly five hundred 

 parts of fat for every hundred in its food, and this fat 

 must be m'ade from proteids or carbohydrates. Whether it 

 <3an come from the latter is still perhaps an open question; 

 for, while all fattening foods are rich in starch or similar 

 bodies, there are considerable chemical difficulties in sup- 

 posing an origin of fats from such; and it is on the whole 

 more probable that they simply act by sparing from use 

 .fats simultaneously formed or stored in the body, and 

 which would have otherwise been called upon. They make 

 glycogen, and this shelters the fats. Liebig, indeed, in a very 

 -celebrated discussion, maintained that fats were formed 

 irom carbohydrates. He showed that a cow gave out more 

 butter in its milk than it received fats in its food; and 

 Huber, the blind naturalist, showed that bees still made 

 wax (a fatty body) for a time when fed on pure sugar; and 

 indefinitely when fed on honey. Consequently, for a long 

 time, an origin of fats from carbohydrates was supposed to 

 be proved; but their possible origin from proteids (a possi- 

 bility now shown to be a certainty) was neglected, and the 

 Talidity of the above proofs of their carbohydrate origin is 

 thus upset. The cow may have made its butter from proteids; 

 the bees, fed on sugar, their wax for a time from proteids 

 in their bodies already; and, indefinitely, when fed on honey, 

 irom the proteids in that substance. Moreover, animals 

 (ducks) fed on abundant rice, which contains much carbo- 

 hydrate but very little proteid or fat, remain lean; while if 

 some fat be added they lay up fat. 



