PURPOSES SERVED BY THE FAT. 597 



dition, the principal purposes served by the fat are simple and the same. 

 It lubricates the joints — covers and protects the internal viscera — keeps 

 the muscles separate, and enables them to play freely among each otiier 

 — makes the hair and skin soft and flexible, — and, by filling up 1 ml lows, 

 contributes to the roundness and plumpness of the parts, and defends the 

 extremities of the bones from external injury. When exercise is taken, 

 a portion of the fat of the body appears to be more or less changed and 

 removed, and is afterwards found in the perspiration, or in the dung. It 

 is to make up for this natural waste that all animak, even when the fat 

 of their body undergoes no increase, require a certain supply to be daily 

 given to them in their food. 



The accumulation of fat in animals seems to be an effort of nature to 

 lay in a store of food in time of plenty, which may be made available in 

 the performance of the usual functions of the animal when a time of 

 scarcity comes. If the food contain too little oil to lubricate the joints 

 and lo supply the natural waste of this kind of matter, then the store of 

 fat which has been accumulated in tjj^ie of plenty is drawn upon, a por- 

 tion of it is worked up, so to speak, and the fat of the body diminishes in 

 quantity. We have seen also that the --espiration of carnivorous animals 

 is supported at the expense of the fat Avhich they eat — and that the lean- 

 ness which attends upon starvation is owing to the fat of the living body 

 beingconsumed in supplying thecarbon given o(f from the lungs. Another 

 purpose, therefore, for which animals seem to be invested with the power 

 of laying on fat, is, that a store of food for the purposes of respiration 

 may be carried about in the body itself, to meet any unusual demand 

 which the food may not be able wholly to supply. 



§ 5. Of the natural waste of the parts of the body in a fall grown animal. 

 We have seen that, if the food of the animal be unable to supply the 

 carbon given off from the lungs, and the fat which the movements of the 

 limbs require, the parts of the body themselves are laid under contribu 

 tion in order to supply these substances. Thus, when the food is stinted, 

 the body necessarily undergoes a waste from this cause. 



But this is not a constant waste. It is prevented by the use of a larger 

 quantity of food. The }:)arts of the body, however, do undergo a con- 

 stant and natural waste, to make up for which is one of the main pur- 

 poses served by the food. 



It has been ascertained by physiologists, that all the parts of the body 

 undergo a slow and insensible process of renewal. The hair and the nails 

 we can see to be constantly renewed. They grow, or are thrust out- 

 wards. But the muscles and even the bones are by little and little re- 

 well as that of its mother, requires. And, lastly, man by eating the fat of the calf can re 

 convert it into margarine and those other fatty substances which are found in the various 

 parts of Ins borly. Substances which can thus so frequently and so readily be changed, the 

 one into the other, must be very cloeely connected, and the mode in which their mutual 

 transformations are effected will, no doubt, prove to be simple when these are rightly im- 

 derstood. 



The chemical reader will understand that it is for the sake of simplicity only that I have 

 in this note compared together the entire fats stearine, margarine, &c., instead of the fatty 

 acids only which they are known to contain. 



The reader will consult with much advantage and satisfaction upon this subject, a work 

 upon ChcmicfU Physiology, by Professor MuMer, of Utrecht, (Procve eener Algemeene Phy- 

 siulo f^sche Scheikunde, p. 2(50, el acq.) of which I am happy to say that a translation from 

 the Dutch is now in progresis by my assistant, Mr. Fromberg, and will speedily be published 

 by the Messrs. Blackwood. 



