Mat H, 1886.] 



SCIENCE. 



445 



matters were received already formed with the 

 food, and that the role of the animal organism 

 was merely to accumulate them. The vegetable 

 organism, it was thought, was alone able to form 

 them. 



In comparing the quantities of fat stored in the 

 bodies of those animals experimented upon with 

 those known to have been introduced w T ith the 

 food, they were found to be considerably greater. 

 It was shown, that, of the thousand grams daily 

 increase in weight of an ox, six hundred or more 

 were due to an accumulation of fat, while the 

 ingested matters contained less than half of that 

 quantity ; so that it is rendered certain that a 

 large proportion, if not all, of the fat in the animal 

 body, is due to sources other than fatty foods. 

 What these sources are, is an important question, 

 the answer to which has not been satisfactory. It 

 has commanded much attention, especially in 

 Germany, within late years, and has given rise to 

 numerous controversies. It is a subject, also, of 

 no little importance, since obesity in man is often 

 an infirmity, and sometimes a grave disease. It 

 will therefore be of interest to present such facts, 

 in connection therewith, as have been so far ex- 

 perimentally demonstrated, as given by A. Sanson 

 in the Revue scientifique. 



Pettenkofer and Voit kept during a number of 

 days, in a suitable respiration apparatus, a dog 

 which received daily given quantities of dried 

 starch and fat, and ascertained that the dog 

 eliminated, under the form of carbonic acid, not 

 only all the carbon of the ingested starch, but also 

 a portion of that of the fat. It was therefore 

 concluded that the starch thus decomposed did 

 not serve in the formation of the fat. This 

 formed the basis of a theory, on Voit's part, that 

 the formatior of fat was due to the reduction of 

 albuminoid matters by the oxygen of respiration. 

 According to this theory, the alimentary sub- 

 stances which we call carbohydrates — that is to 

 say, starch, glycogen, sugars — take no part what- 

 ever in the formation of fat. These are decom- 

 posed in the organism, furnishing material for 

 the animal heat, and resolving themselves into 

 carbonic acid and water. The albuminoid mat- 

 ters — the proteines — are only in part thus de- 

 composed, and furnish, besides, urea and fat. 



This theory of Voit, which was in reality a very 

 ingenious hypothesis, was immediately accepted 

 throughout Germany, though Henneberg showed 

 by chemical calculation that 100 grams of al- 

 bumen thus used would not furnish more than 51 

 grams of fat in addition to 33 of urea and 27 of 

 carbonic acid. It is necessary to remark, how- 

 ever, that, in the numerous experiments per- 

 formed by Voit and Ins disciples in support of 



this hypothesis, they were not able to verify it 

 directly. It is impossible, in fact, to sustain the 

 life of an animal nourished exclusively by albu- 

 men. 



Taking as a point of departure the data of 

 Hermeberg's calculations and the facts established 

 by the experiments, it has not been difficult to 

 show that Voit's hypothesis is inadmissible by rea- 

 son of its impossibility. The geese upon which 

 Persoz experimented were found to have formed 

 over 4,000 grams of fat, while their food, com- 

 pletely deprived of fat, contained but 1,400 grams of 

 proteine, — a quantity sufficient to form but a lit- 

 tle more than 700 grams of fat. Other experi- 

 ments of the same nature show the impossibility 

 even in a more striking degree. A cow which 

 gained at the rate of 1,600 grams per day stored 

 up daily nearly 1,000 grams of fat, but an analysis 

 of the food with which she was supplied showed 

 only sufficient albuminoid matters to furnish 

 about half that quantity. 



These and other experiments have established 

 reasons, now generally received, for the belief 

 that herbivorous animals do not depend upon 

 albuminous foods for the sources of fat, but that 

 the fat is in a large part derived from the carbo- 

 hydrates. 



Very lately Riibner has repeated the researches 

 of Pettenkofer and Voit, and reached opposite 

 results. He placed in the respiration apparatus 

 a small dog weighing a little more than six kilo- 

 grams, and gave it food composed of 85 grams of 

 starch, 100 grams of cane-sugar, and 4.7 grams of 

 fat. During ten days, in which it was kept under 

 these conditions, it was found to have eliminated 

 87 grams of carbon. The entire quantity of car- 

 bon introduced by the food was 176 grams, of 

 which 89 were retained in the organism, and 

 served in the formation of fat, 76 of which must 

 have been derived from the carbohydrates. From 

 these facts he concludes that the carbohydrates 

 are demonstrated to be a source of fat in the car- 

 nivores as well as in the herbivores and omnivores. 

 These researches of Riibner destroy absolutely the 

 value of those by Pettenkofer and Voit ; and one 

 can feel assured that the German theory of the 

 dependence exclusively upon albuminoid mat- 

 ters in the formation of fat in the animal organ- 

 ism will no longer obtain acceptance. In these 

 organisms, as in the vegetable, the fatty matters 

 are formed by the carbohydrates furnished in 

 abundance in the food. 



No more definite conclusions, however, in re- 

 gard to the proper composition of food to produce 

 fattening, can be reached from a knowledge of 

 these facts. In alimentation every thing depends 

 upon digestion. Every thing must be adapted to 



