CHAPTER IV. 



NUTKITION STUDIES— THE FUNCTIONS OF PROTEIN, CARBO- 

 HYDRATES, AND FAT. 



In this chapter there will be considered the effects of withhold- 

 ing all food from the animal and of feeding the three basic nutri- 

 ents — proteins, carbohydrates, and fat — separately and in combi- 

 nation. 



74. Starvation. — At all times there is a loss of nitrogen from the 

 animal body by way of the urine, since all the tissues are steadily 

 breaking down and wasting away. The nitrogen excretion from 

 the body of a well-nourished animal is relatively large, keeping 

 pace with the amount of nitrogen supplied in the food. If food is 

 withheld from such an animal the nitrogen excretion decreases 

 rapidly at first, many holding that the losses at this time fall chiefly 

 upon the circulating protein, or protein w^hich is not a part of the 

 tissues of the body. If starvation continues, this loss falls upon 

 both the circulating protein and on the muscles and other nitroge- 

 nous tissues of the body. At the same time the fats of the body 

 are also being gradually oxidized or burned in the effort to sustain 

 life. The nitrogen waste in the urine now slowly decreases until 

 it reaches a minimum, which remains quite constant so long as 

 there is available fatty matter to furnish energy. When the supply 

 of body fat begins to fail, however, the muscles and other protein 

 tissues waste more rapidly, and the animal finally perishes thru 

 the impairment of its organs and the lack of the food fuel re- 

 quired to carry on the functions of life. 



A rise in temperature occurs at the beginning of starvation, fol- 

 lowed by a general fall until death takes place. Carnivora or 

 flesh-eating animals can withstand hunger longer than herbivora. 

 While dogs and cats have lived until their weights were decreased 

 33 to 40 per et., horses and ruminants will die when their weight 

 has been reduced 20 to 25 per ct.^ The age of the animal also in- 

 fluences the time at which death occurs from starvation, old ani- 

 mals withstanding the effects of hunger better than young ones, 

 the latter losing weight more rapidly and dying after a smaller loss 

 of weight than old ones.^ 



* M. Wilckens in v. d. Goltz, Hand. d. ges. Landw., Ill, p. 88. 

 » Halliburton, Chem. Physiol., p. 834. 



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