THE METABOLISM OF FAT 439 



the respiratory quotient, which for carbohydrate is 1, and under 1 

 for proteins and fats, rises well above 1 e.g., to 1-3 or 1-4. At first 

 the discrepancy was attributed to experimental error, but the ex- 

 planation now generally accepted is that carbohydrate is being turned 

 into fat, and that in the process carbon dioxide is liberated, so that the 

 respiratory quotient is raised above 1. The following formula sum- 

 marizes the series of chemical changes which bring about this result : 



13C 6 H 12 6 = C 55 H 101 6 + 23C0 2 + 26H 2 



Fat from Protein. The question as to the formation of fat from 

 protein is a vexed one. It cannot be denied that such a forma- 

 tion is possible within the organism. From the amino-aeids arising 

 from autolyzed body protein or from digested protein the formation 

 of carbohydrate may take place, and from this carbohydrate fat may 

 well be formed. From the available evidence it would appear that, 

 although such a formation is possible, the animal body under normal 

 conditions doas not make use of this power. 



Under certain conditions, however, such as the. development of 

 larvae, the formation after death of a waxy body known as adipooere, 

 and possibly in some cases of so-called fatty degeneration during 

 life, such a transformation of amino-acids into fat does take place. 

 It has been shown, for example, that some of the higher non- volatile 

 fatty acids are formed when the larvae of the blowfly, Calliphora, are 

 rubbed with Witte's peptone into a homogeneous mass. So, too, it 

 has been shown that fly-maggots, estimated from controls to contain 

 a known quantity of fat, when allowed to feed on blood of a known fat 

 content, develop after a time much more fat than existed in them- 

 selves and the blood together at the start of the experiment. Such 

 experiments have not been accepted, owing to the fact that fat may 

 result in the blood from bacterial decomposition. Recent researches, 

 however, tend to confirm rather than discount these results. 



In regard to the formation of adiposere, this is a wax-like m'xture 

 of insoluble soaps, fatty acids, and ammonia, which is found in corpses 

 exposed to water. It is quite possible that lower organisms may also 

 play a part here, and its development from the body proteins is by 

 no means proved. Positive results have bean claimed from feading 

 experiments, but it has been pointed out that the calculations giving 

 these were based upon a wrong assumption of the proportion which 

 nitrogen bears to carbon in the meat fed. When the calculations are 

 corrected, the formation of fat from protein is found to be unproven. 

 The evidence of the most recent feeding experiments is contradictory, 

 some observers claiming that a formation of fat from protein can be 

 shown, others denying this. 



From what has been said above, we may conclude that there exists in 

 omnivora no fat rigidly characteristic of each type of animal, for foreign 

 fats may be stored as such. Recent work, however, is tending to 

 show that an animal's own characteristic fat is formed from carbo- 

 hydrate just the same as a plant's characteristic fat or oil is formed 

 from these bodies. Different species of animals form a different fat 



