no THE CHEMISTRY OF CATTLE FEEDING 



are constantly going on in animal bodies. The tissues are 

 exposed to a continuous process of oxidation by which they 

 are gradually attenuated. At the same time, the blood is 

 constantly being enriched by materials derived from the food, 

 and these are used to repair the waste, and form new tissues. 

 These two processes of elaboration and attrition constitute the 

 very essence of life as we know it. A condition of equilibrium 

 may be established between the two ; but if the former takes 

 place faster than the latter, the mass of the body will be 

 increased, and vice versa. 



It is not a little remarkable that these two opposite kinds 

 of change should be carried on by the same agency. It is 

 difficult to understand why the oxidisable material derived 

 from the food, and the oxidising agent formed in the lungs, do 

 not react, when, ex hypothesis, they are both present in the 

 blood at the same time. As a matter of fact many authorities 

 hold that they do react, i.e. that the food materials are directly 

 oxidised in the blood, and merely serve to protect the per- 

 manent tissues from oxidation. According to this view, a 

 sufficient quantity of food materials would afford complete 

 protection, and any less quantity only a partial protection. 

 In the latter case there would be a proportional loss of body 

 weight owing to oxidation of the tissues. On the other hand, 

 if the food materials were more than sufficient to reduce the 

 oxyhsemoglobin, the excess could be stored up as tissue, 

 and the mass of the body would be increased. 



As against this, however, there is reason to believe that 

 the tissues actually do suffer continuous oxidation, and are 

 as continuously renewed in the manner described. Otherwise, 

 a sufficiency of fat arid carbohydrate food would completely 

 protect the protein tissues from oxidation; but it has been 

 proved that such is not the case. Huxley inclines to the 

 view that the food material is not directly oxidised in the 

 blood, but only after it has been deposited as tissue. In 

 that case, probably, the fat and carbohydrates of the food 

 would afford no protection to the protein tissues at all, whereas 

 it has been proved that they do protect them against oxidation 

 to a very considerable extent (p. 133). 



