160 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



termed accessory foods, and have but little bearing on the study of 

 nutrition in the domestic animals. 



Blood is the chief nutritive fluid of animals. What, therefore, is to 

 be converted into tissue must first be converted into blood; consequently, 

 the substances taken in food must be converted into blood, or, at least, 

 pass into the blood, to be of nutritive value. Blood Contains about 80 

 per cent, of water and 20 per cent, of solids. Of the latter, 1£ per cent, 

 is organic, consisting of albuminous bodies, fats, and carbo-hydrates, the 

 latter being represented by glucose and occurring in small quantities. 

 Blood, therefore, contains all the constituents of the tissues and the 

 elements for their formation, so arranged as to require but slight chem- 

 ical modification to transform them into tissue. Blood consequently 

 contains, in suitable form, all the organic elements necessary for the 

 formation of all the animal tissues and fluids. The constituents of the 

 blood and flesh of the carnivora are absolutely identical with the constit- 

 uents of the blood and flesh of those animals which serve as their food. 

 The nutritive processes of the carnivora consist, therefore, in a simple 

 nutritive conversion of the blood and flesh of herbivora. Suckling 

 animals, whether herbivorous or carnivorous, obtain in milk what might 

 be regarded as the equivalent of the flesh of their mother, since milk 

 contains representatives of all the constituents of blood, casein and 

 albumen representing the albuminous group, butter the fats, and milk- 

 sugar the carbo-hydrates. The same inorganic salts are also found in the 

 milk as in the blood, and water is present in large amount. 



In the herbivora the nutritive processes are not less simple, since all 

 parts of plants which serve as their food contain representatives of albu- 

 minous, carbo-hydrate, and fatty tissue-constituents which are similar, or 

 almost identical, to those found in the animal tissues. Consequently, the 

 vegetable bodies which serve as foods for animals contain, read}^ formed, 

 the constituents of animal tissues, and the nutritive value of vegetable 

 foods is in direct relation to the proportion of these substances present. 

 It may therefore be said that animals are dependent upon the inorganic 

 matters of the earth and air for their food-stuffs ; for from these inor- 

 ganic constituents of the earth's surface plants indirectly create the blood 

 and flesh of herbivora, and in the blood and flesh of herbivora the car- 

 nivora, in a strict sense, may be said only to obtain matter of vegetable 

 origin with which the former were nourished. Animals, therefore, through 

 the mediation of plants are built up out of C0 2 , H 2 0, NH 3 , N0 3 H, and a 

 few other inorganic compounds (Gorup-Besanez). 



What has been said about the renewal of the organic tissue-elements 

 might be repeated for the inorganic tissue-constituents of animals. These 

 are also obtained, ready prepared and ready for assimilation, by both 

 carnivora and herbivora. The inorganic constituents of the blood of the 



