94 1^**'*' * PHYSIOLOGY FOR DENTAL STUDENTS. 



such as creatin also make their appearance in the urine, and 

 there is an increase in the excretion of ammonia, indicating that 

 larger quantities of free acid are being set free in the organism. 



Starvation ends in death in an adult man in somewhat over 

 four weeks, but much sooner in children, because of their more 

 active metabolism. At the time of death the body weight may 

 be reduced by 50 per cent. The body temperature does not 

 change until within a few days of death, when it begins to fall, 

 and it is undoubtedly true that if means be taken to prevent cool- 

 ing of the animal at this stage, life will be prolonged. 



Normal Metabolism. Apart from the practical importance 

 of knowing something about the behavior of an animal during 

 starvation, such knowledge is of great value since it furnishes a 

 standard with which to compare the metabolism of animals under 

 normal conditions. Taking again the nitrogen balance as indi- 

 cating the extent of protein tear and wear in the body, let us 

 consider first of all the conditions under which equilibrium may 

 be regained. It would be quite natural to suppose that if an 

 amount of protein containing the same amount of nitrogen as 

 is excreted during starvation were given to a starving animal, 

 the intake and output of nitrogen would balance. We are led 

 to make this assumption because we know that any business bal- 

 ance sheet showing an excess of expenditure over income could 

 be met by such an adjustment. But it is a very different matter 

 with the nitrogen balance sheet of the body; for, if we give the 

 starving animal just enough protein to cover the nitrogen loss, 

 we shall cause the excretion to rise to a total which is practically 

 equal to the starvation amount plus all that we have given as 

 food, and although by daily giving this amount of protein there 

 may be a slight decline in the excretion, it will never come near 

 to being the same as that of the intake. The only effect of such 

 feeding will be to prolong life for a few days. 



To strike equilibrium we must give an amount of protein whose 

 nitrogen content is at least two and one-half times that of the 

 starvation level. For a few days following the establishment of 

 this more liberal diet, the nitrogen excretion will be far in ex- 

 cess of the income, but it will gradually decline until it corre- 



