266 AMERICAN AGRICULTURE. 



with the blood, is by it, diffused throughout the whole frame. 

 The effect is precisely analogous to the combustion of fuel, 

 oils, &c. in the open air. 



Perspiration is the counteracting agent which modifies this 

 lit, and prevents the injurious effects which under exposure 

 to great external heat, would insure certain destruction. And 

 this too, it will have been seen, is provided at the expense of 

 the animal food. When from excessive heat, caused by vio- 

 lent exercise or otherwise, by which respiration is accelerated 

 n'nl the animal temperature becomes elevated, the papillae 

 of the skin pour the limpid fluid through their innumerable 

 s which in its conversion into vapor, seize upon the ani- 

 .1 heat and remove it from the system, producing that de- 

 icious coolness so grateful to the laboring man and beast in a 

 sultry summer's day. These two opposing principles, like 

 t !; antagonistic operations of the regulator in mechanics, 

 keep up a perfect balance in the vital machine, and enable 

 tin* entire division of the animal creation distinguished as 

 warm blooded, including man and the brute, all the feathered 

 tribes, the whale, the seal, the walrus, &c., to maintain an 

 equilibrium of temperature, whether under the equator or the 

 p.'es, on the peaks of Chirnborazo, the burning sands of 

 X:ihara, or plunged in the depths of the Arctic Ocean. 



The connexion between the size of the lungs, and the ap- 

 titude of animals to fatten, will be more apparent from the 

 fact, that the carbon and hydrogen which are abstracted, 

 constitute two of the only three elements of fat. The lar- 

 ger si/* 1 , the fuller play, and the greater activity of the lung, 

 by exhausting more of the materials of fat, must necessarily 

 diminish its formation in the animal system ; unless it can 

 j-hown, which has never yet been done, that the removal of 

 :i pnrton of the fat-forming principles, accelerates the assimi- 

 lation of the remainder. 



The food which supplies respiration in the herbivorous ani- 

 mals, alter they :uv deprived of the milk which furnishes it 

 .iiiular.ee, is the starch, gum, sugar, vegetable fats and 

 ci's, which exist in the vegetables, grain and roots which 

 thry consume ; ;uul in certain cases where there is a defi- 

 eieney of ether food, it is sparingly furnished in woody and 

 cellular fibre. All these substances constitute the principal 

 part of dry vegetable food, and arc made up of these elements, 

 which in starch, gum, cane-sugar and cellular fibre, exist in 

 precisely the same proportions, viz : 44 per cent, of carbon, 

 <>. 2 of hydrogen and 49.8 of oxygen. Grape sugar, woody 



