412 THE SUPPORTING TISSUES. 



then killed and analyzed. The result showed that they contained 

 an amount of fat which was from seven to eleven times as large 

 as the total amount of fat in the blood, plus the amount which they 

 originally contained. 



Of the manner in which the fat originates from albuminous 

 material our knowledge is still imperfect. That an actual libera- 

 tion of fatty radicles can occur directly appears unlikely, as we 

 have no evidence whatever to show that the albuminous molecule 

 contains radicles with more than six or nine atoms of carbon. We 

 have shown, however, that glucose and glycogen can both be 

 derived from this source. The question hence suggests itself, Is it 

 possible that the formation of fats from albumins takes place with 

 the intermediate formation of carbohydrates ? As a matter of fact, 

 this possibility is now well established. This transformation repre- 

 sents one of the most important synthetic phenomena which occur 

 in the animal world, and is of the nature of a synthetic reduc- 

 tion in which the CHOH groups of the carbohydrates are trans- 

 formed into CH 2 groups. 



Magnus-Levy has recently suggested that the natural synthesis 

 of fats from carbohydrates takes place by way of lactic acid and 

 acetic aldehyde in such manner that the higher fatty acids result 

 through repeated condensation of acetic aldehyde or croton aldehyde 

 groups and subsequent reduction. 



The possible origin of fats from carbohydrates can be demon- 

 strated in various ways. Two animals from the same litter and 

 approximately of equal weight are starved until the stored fat 

 has mostly disappeared. The one is then killed so as to ascertain 

 the amount of albumins and fats which still remain. The other 

 animal is fed with a definite quantity of some cereal, the con- 

 tained amounts of albumins, starch, and fat of which are known. 

 The feces are carefully collected and the amount of non-resorbed 

 fat and albumins ascertained. After a variable period of time this 

 animal also is killed, and the amount of albumins and fat esti- 

 mated. The increase in the amount of albumins must, of course, 

 be referable to that ingested, while the increase in the fat may be 

 in part due to the ingested fat, in part to albumins, and in part to 

 carbohydrates. In such cases it has been found that the amount of 

 both albumins and fat which were contained in the food are by 

 no means sufficient to account for all the accumulated fat, so 

 that the conclusion is unavoidable that a certain proportion of this 

 must be referable to the ingested carbohydrates. Calculation has, 

 indeed, shown that as much as 86.7 per cent, of the fat is of such 

 origin. 



Significance of the Fats. As regards the function of fat in the 

 animal body our knowledge is very imperfect. Owing to its 

 property as a poor conductor of heat, it is probably of moment 

 in preventing undue irradiation. Its principal significance, 



