1846.] Feeding of Cattle. 305 



upon many and varying circumstances. In an easy respiration 

 the quantity of air taken into the chest of a man is about 15 or 

 18 cubic inches; in winter th€ air, being condensed, will con- 

 tain, bulk for bulk, more oxygen than in summer, when the air 

 is expanded; this remark applies with an equal degree of truth, 

 to warm and cold climates. In addition to a numerous train of 

 modifying causes dependent on the preceding facts regarding the 

 consumption of oxygen, numerous others exist dependent upon 

 peculiar circumstances under which the animal may be placed. 

 4-11 motion is attended with accelerated respiration, and conse- 

 t]uently the formation of an additional amount of carbonic acid; 

 and it has already been shown how temperature influences this 

 process. 



It is, then, to support this important function that the non- 

 azotized elements are employed in a great measure; the residue 

 serves another purpose, namely, the foimation of fat, of which we 

 have to speak presently. The preponderance of carbon in these 

 proximate elements, over their other constituents would point 

 them out as the most fit for the purposes of respiration. Their 

 constitution is thus: 



Fat : 10 C+10 II+O 

 Starch : 12 C-f 10 H+10 

 Sugar : 12 C+9 H-f 9 

 Alcohol : 4 CX6 H-f 2 



It remains for us now briefly to consider the chemical and phy- 

 siological relations of fat. 



Fat is a peculiar substance deposited in all parts of the body, 

 in the cells of the cellulcir tissue, and apparently requiring no 

 special structure for its formation. It is composed of three fatty 

 acids, namely, stearic, margaric, and oleic acids, in combination 

 with a peculiar organic base, (glycerine.) These acids vary in 

 different kinds of fat; the first abounding in the hard, the second 

 in the soft, and the third in the liquid fats and oils. Some fats 

 contain peculiar substances, as that of the brain which contains 

 phosphorus. 



Some difference of opinion exists regarding the production of 

 fatty material in the animal economy. The French chemists 

 seem inclined to consider that all the fat found in the body is de- 

 rived from the substances taken as food .containing fat; in fact, 

 that fat is furnished to the system ready formed. The gramini- 

 vorous tribes take it in ready formed with their food, and carnivo- 

 rous animals, in whom, however, it is usually very scanty, derive 

 it from them; therefore, certainly, directly or indirectly, the fat 

 of an animal is derived from the fats, oils, wax, kc, more or less 

 of which exists in our vegetable food. But as it is an undoubted 



