586 Journal of Agriculture. [8 Oct., 1907. 



THE ELEMEiNTS OF ANIMAL PHYSIOLOGY. 



TI'. .4. Osborne, M.B., D.Sc, Professor of Physiology and Histology,. 

 Dean of tlie Faculty of Agricilturc in the University of iMelboiirne. 



{Continued from page 46"/.) 



CHAPTER IX. 



Animal Nutrition. 



An animal that has reached adult life and is not increasing in weight 

 must nevertheless eat, digest and absorb food which, as we have seen, 

 serves as material for renewal and repair and for the supply of energy. 

 In dealing with this subject it will be advisable to consider, the essential 

 ingredients of food, the adventitious ingredients of food, the essential 

 qualities of food, food required for growth, and finally the composition of 

 various natural foods. 



The Essential Ingredients of Food. . 



I. Repair Food. — Every living cell in the bodv is in a state of con- 

 stant repair requiring a continual intake of fresh material. Moreover there- 

 are constant losses of complex material from the skin, such as the protein 

 of sebum, hairs, and the outer layers of the skin itself. In lactating. 

 animals the secretion of milk is a heavy drain on many constituents of the 

 body. Water is continually being excreted by the kidney, lung, and skin, 

 and salts leave the body in the urine. All these materials must be present 

 in the food consumed. 



Water is present in all foods. Hay may contain as much as 13 per 

 cent., oats about 18 per cent., green fodders vary between 60 and 80 per 

 cent., and roots and tubers as much as 90 per cent. If the water taken 

 in these foods is not sufficient then thirst is provoked and water is in- 

 stinctively taken by the animal. The rule holds with the domestic animals 

 as with man that the water supplied for drinking purposes should be 

 pure and fresh and above suspicion. 



Salts of soda, potash, fime, magnesia, phosphorus, and iron are all 

 in the body, are constantly leaving the body and so' must be supplied in 

 the food. The various foods eaten by different animals are all fairly 

 rich in salts, but with grazing animals there is sometimes a danger that 

 too little common salt or sodium chloride may be present ; for vegetable 

 foods, though rich in potash salts, are poor in soda salts. This is par- 

 ticularly the case the more distant from the sea the grazing country is. 

 Hence the instinctive relish with which most herbivorous animals lick 

 common salt if placed within their reach. In lactating animals there is 

 a considerable loss of lime in the milk, for this fluid contains actually 

 more lime than does lime water. The amount of lime in oats and maize- 

 kernels is very small, roots also are somewhat poor in this constituent, 

 but clovers are rich and to a lesser degree the grasses. Animals fed on 

 salt free foods die speedily ; even a poverty in one salt constituent will 

 lower vitality and cause emaciation, skin trouble and feeble resistance to 

 disease. Equallv dangerous is a salt content much above what is in the 

 animal's natural food. 



