556 ABNORMALITIES IN METABOLISM 



The carbonate thus formed goes back to the tissues to combine again 

 with more CO2 and form bicarbonate. If acids are introduced into 

 the blood they combine with the alkahes there, forming neutral salts 

 which are ehminated in the urine, and in this way the amount of 

 alkali in the blood is reduced, with a consequent reduction in the 

 capacity of the blood to carry CO2 away from the tissues; the amount 

 of CO2 in the blood sinking to as low as 2.5 and 3 per cent. (Walter). 

 Consequently, in acid poisoning the CO2 produced in metabolism ac- 

 cumulates in the tissues where it is formed, and blocks the processes 

 of oxidation, so that the animal suifers from asphyxia exactly as if it 

 were deprived of air. In other words, the lack of alkalies in the blood 

 in acid intoxication checks the "internal respiration," as intracellular 

 gas exchange is called, by preventing the removal of CO2 from the cells. 

 The acids stimulate the respiratory center, which is extremely sensitive 

 to them, and the increased respiration tends to reduce the aciditA^ by 

 getting rid of the CO2, but under the conditions of the experiment 

 this is not sufficient to prevent asphyxia. 



If the urine of such an animal is analyzed, it is found to contain 

 increased quantities of the four chief inorganic bases, Na, K, Ca, and 

 Mg (the last two apparently being derived from the bones) ;" but in 

 addition to these it is found that the amount of ammonia in the urine 

 is decidedly increased. If instead of a rabbit a carnivorous animal, 

 such as a dog, is given acids, it will be found relatively insusceptible, 

 so that much larger quantities can be given without causing acid 

 intoxication. Examination of the urine of such a dog will show that 

 the elimination of ammonia is increased much more than it is in the 

 herbivora, while the inorganic alkalies are increased but little. From 

 this it is deduced that in acid intoxication part of the nitrogen that 

 normally goes to form urea becomes, while in the antecedent form of 

 ammonia, combined with part of the acid that has entered the blood. 

 In this way much of the neutralization of the acids is accomplished 

 by ammonia, and the inorganic alkalies of the blood are spared. As 

 in carnivora the amount of protein metabolism is much greater and 

 more rapid than in herbivora, the ammonia available for neutral- 

 ization of acids is much greater than in the latter, and hence the rela- 

 tive lack of susceptibility of carnivora to acid poisoning.'^'' The 

 proteins of the blood also combine some of the acid, perhaps one-fifth 

 of the neutralizing capacity of the ])lood being attributable to tliom. 

 Another factor is the possible accunuilation of acids within the cells, 

 which must modify greatly any conclusions based upon studies of the 

 blood and urine. It is within the cells that the effects of acids must 

 be manifested, and it is perfectly possible, and indeed almost certain, 



" See Goto, Jour. Biol. Clieni., 1918 (36), 355. 



'* This hiis been nicely shown by Eppingor (^^'i('n. kliii. \\'oi'li., ll>()('» (H>), 111), 

 who found that udministnition of considerahle quantities of amino-acids (glycine 

 alanine, aspartic acid) to ral)])its greatly increased tiieir resistance to acid intoxica- 

 tion, i)resunial)]y by yielding ninnionia through normal stc'jis of protein metabolism. 



