724 METABOLISM 



animals are artificially warmed, protein metabolism becomes increased; 

 and (3) toxic protein-decomposition products specifically causing an ex- 

 cessive breakdown of protein. 



Although there is increased protein breakdown during fever, it must 

 not be forgotten that only about 20 per cent of the total expenditure 

 of the body is derived from this foodstuff, 80 per cent coming from non- 

 nitrogenous material, which must be fat, because the available carbo- 

 hydrates are used up at an early stage. 



Since the general metabolism is increased, the excessive breakdown of 

 the fatty substances, occurring as it does in the presence of a diminished 

 combustion of carbohydrates, interferes with the proper oxidation of the 

 fatty-acid molecules and leads to the appearance of so-called acidosis 

 products in the urine, and consequently to a relative increase in the 

 urinary ammonia (page 616). A tendency to acidosis therefore exists. 

 The acidosis may reach a considerable degree of severity and cause tlio 

 tension of carbon dioxide in the alveolar air to become diminished. Since 

 a similar degree of acidosis may be produced in partially starved ani- 

 mals by overheating them with moist air, but not so if the animals are 

 liberally fed with carbohydrates; it is probably safe to conclude that 

 abundance of carbohydrate is advisable in the food that is furnished to 

 fever patients. 



Another interesting metabolic change in fever concerns the salt bal- 

 ance. This is studied by observing the amount of sodium chloride excreted 

 by the urine. As is well known, this becomes markedly diminished until 

 the crisis of the fever, when it suddenly increases. Salt retention is more 

 marked in certain types of fever than in others, and it is essentially dif- 

 ferent in nature from the salt retention that has been observed to occur 

 in nephritis. This difference has been brought to light by examination 

 of the chloride content of the blood. In nephritis, the concentration of 

 chlorides in the blood is considerably increased, whereas in fever it is 

 markedly diminished. The deficiency in salt elimination can not be at- 

 tributed to a deficiency of salt in the food, for it sets in before the diet 

 has been curtailed and, when salt is given to a febrile patient, it is re- 

 tained in the body to a greater degree than is the case in the normal 

 individual. For some reason the tissues in fever have acquired the 

 property of- retaining large quantities of salt. 



Attempts to study the water balance during fever have frequently been 

 made, but the technical difficulties of such investigations make the re- 

 sults uncertain and of little value. That some retention of water occurs 

 during fever is, however, evidenced by the dilution of the blood. At the 

 crisis this hydremia quickly disappears at the same time as the increased 



