DOMESTIC ANIMALS. 267 



fibre, and vegetable and animal fats and oils are made up of 

 the same elements, but in different proportions, the last con- 

 taining much more carbon and hydrogen than those above 

 specified. In the fattening animals, it is supposed the vegeta- 

 ble fats and oils are immediately transferred to the fat cells, 

 undergoing only such slight modification as perfectly adapts 

 them to the animal economy, while respiration is supplied by 

 the other enumerated vegetable matters. If these last arc taken 

 into the stomach beyond the necessary demand for its object, 

 they too are converted by the animal functions into fat, and 

 are stored up in the system for future use. But if the supply 

 of the latter is insufficient for respiration, it first appropriates 

 the vegetable fat contained in the food; if this is deficient, it 

 draws on the accumulated stores of animal fat already secre- 

 ted in the system, and when these two are exhausted, it sei- 

 zes upon what is contained in the tissues and muscle. When 

 the animal commences drawing upon its own resources for 

 the support of its vital functions, deterioration begins; and if 

 long continued, great emaciation succeeds, which is soon 

 followed by starvation and death. The carnivorous animals 

 are furnished with their respiratory excretions, from the ani- 

 mal fat and fibre which exist in their food, and which the 

 herbivorae had previously abstracted from the vegetable 

 creation. 



The circumstances which augment respiration are exercise, 

 cold and an abundant supply of food. Exercise, besides 

 exhausting the materials of fat, produces a waste of fibre and 

 tissue, the muscular and nitrogenized parts of the animal 

 system ; and it is obvious from the foregoing principles, that 

 coid requires a corresponding demand for carbon and hydro- 

 gen to keep up the vital warmth. The consumption of food 

 to the fullest extent required for invigorating the frame, cre- 

 ates a desire for activity and it insensibly induces full respi- 

 ration. The well-fed, active man unconsciously draws a 

 full, strong breath ; while the abstemious and the feeble, 

 unwittingly use it daintily, as if it were a choice commodity 

 not to be lavishly expended. If the first be observed when 

 sleep has effectually arrested volition, the expanded chest 

 will be seen heaving with the long-drawn sonorous breath ; 

 while that of the latter will exhibit the gentle repose of the 

 infant on its mother's breast. The difference between the 

 food of the inhabitants of the polar and equatorial regions, is 

 strikingly illustrative of the demands both for breathing and 



