364 I>IET OF MIXTURE OF FLESH AND FAT. 



The direct introduction of grape- and cane-sugar into the blood does not increase the amount 

 of used, but the amount of C0 2 is increased. [The doctrine of Liebig, that the oxygen taken 

 in is a measure of the metabolic processes, is refuted by these and other experiments. It 

 would seem that fat is not directly oxidised by 0, but that it is split up into other simpler 

 compounds which are slowly and gradually oxidised ; in fact, fat may lessen the amount of 

 taken in, as it diminishes waste.] 



240. FLESH AND FAT, OR FLESH AND CARBOHYDRATES. An 



amount of flesh equal to -fa to J$ of the weight of the body is required to nourish a 

 dog, which is fed on a purely flesh diet ; if the necessary amount of fat or carbo- 

 hydrates be added to the diet, a smaller quantity of flesh is required (v. Voit). For 

 100 parts of fat added to the flesh diet, 245 parts of dry flesh or 227 of syntonin 

 can be dispensed with. If instead of fats carbohydrates are added, then 100 parts 

 of fat = 230 to 250 of the latter (Jiutmer). When the amount of flesh is insufficient, 

 the addition of fat or carbohydrates to the food always limits the decomposition of 

 the animal's own substance. Lastly, when too much flesh is given along with 

 these substances, the weight of the body increases more with them than without 

 them. Under these circumstances, the animal's body puts on more fat than flesh. 

 The consumption of in the body is regulated by the mixture of flesh and non- 

 nitrogenous substances, rising and falling with the amount of flesh consumed. It 

 is remarkable that more O is consumed when a given amount of flesh is taken, than 

 when the same amount of flesh is taken with the addition of fat. 



It seems that, instead of fat, the corresponding amount of fatty acids has the same effect on 

 the metabolism. [If a dog be fed with fatty acids and a sufficient amount of proteid, no fatty 

 acids are found in the chyle, while fat is formed synthetically, the glycerin for the latter prob- 

 ably being produced in the body.] They are absorbed as an emulsion just like the fats.. 

 "When so absorbed, they seem to be reconverted into fats in their passage from the intestine to 

 the thoracic duct probably by the action of the leucocytes (J. Munk, Will). [Glycerin in small 

 doses has no etFect on the metabolism of proteid, but in large doses it increases it. It is con- 

 sumed in the body, as shown by experiments on the respiratory products, and it prevents 

 a certain amount of fat from being used up. About 20 per cent, is excreted in the urine 

 (Anischink).] 



241. ORIGIN OF FAT IN THE BODY. I. Part of the fat of the body is 

 derived directly from the fat of the food, i.e., it is absorbed and deposited in the 

 tissues. This is shown by the fact that, with a diet containing a small amount of 

 albumin, the addition of more fat causes the deposition of a larger amount of fat 

 in the body (v. Voit, I/ofmann). 



[Hofinann starved a fat dog for 30 days until all its fat was used up. He fed it on lard and 

 a little albumin for 5 days and then killed it. In 5 days it absorbed 1854 grms. of fat and 254 

 grins, of albumin. It added to its body 1353 grms. of fat; but this amount could not be 

 formed from the proteids of the food, and therefore the fat must have come from the fat of the 

 food. Pettenkofer and Voit arrived at the same result in another way. They fed dogs on fish 

 and much fat, and by their respiration apparatus estimated the gaseous income and expendi- 

 ture ( 122). All the N taken in reajypearcd in the excreta, but not all the C. The amount of C 

 retained was very large, therefore a non-nitrogenous residue must have been laid up in the body, 

 and it could only be fat, as this was the only substance found in large amount in the body. 

 They estimated the possible amount of fat that could be formed from the proteids, and found that 

 the amount stored up was far greater than this ; so that the fat of the food must have been 

 stored up in the tissues.] 



Lebedeff found that dogs, which were starved for a month, so as to get rid of all their own 

 fat, on being fed with linseed oil, or mutton suet and flesh, had these fats restored to their 

 tissues. These fats, therefore, must have been absorbed and deposited. J. Munk found the 

 same on feeding animals with rape-seed oil. Fatty acids may also contribute to the formation 

 of fats, as glycerin when formed in the body must be stored up during metabolism {J. Munk). 



Fatty acids may contribute to the formation of fats by union with the glycerin of the body 

 during the metabolism. 



II. A second source of the fats is albuminous bodies. In the case of the forma- 

 tion of fat from proteids, which may yield 11 per cent, of fat (according to Henne- 

 berg 100 parts of dry albumin can form 51 '5 parts of fat), these proteids split up 

 into a non-nitrogenous and a nitrogenous atomic compound. The former, during 



