'ACTION AND USES OF SALICYLIC ACID, ETC. 493 



nervous system is unknown. Therapeutic quantities often 

 cause, in man (salicylism), ringing in the ears and headache. 



Respiration. — The respiratory movements are primarily 

 quickened by the stimulation of the peripheral vagi and 

 respiratory centres produced by sodium salicylate and sali- 

 cylic acid ; but aftpr large doses the respiratory centres are 

 depressed and paralyzed and death takes place by asphyxia. 



Temperature. — Medicinal 'doses do not influence the 

 normal temperature of healthy animals, but do often lower 

 bodily heat in fever, and frequently induce sweating. The 

 largest therapeutic doses must be given to secure an antipy- 

 retic action. Antipyresis occurs from heat loss due to dila- 

 tion of cutaneous blood vessels. 



Kidneys and Elimination. — Salicylic acid, salicin and 

 sodium salicylate circulate in the blood as sodium salicylate 

 and are eliminated in the urine as salicyluric and salicylic 

 acids. This happens in this wise: Some of the salicylic 

 acid of sodium salicylate combines with glycocoll in the 

 body and forms salicyluric acid. HC7H5O3 -|- CgHjl^Oo 

 (glycocoll) = HC9HgIsr04 (salicyluric acid) + HgO ; while 

 some of the sodium salt is decomposed by phosphoric acid in 

 an acid urine into salicylic acid. Like quinine, the excretion 

 of salicylic acid begins soon and goes on slowly. Therefore 

 large doses given continuously may accumulate in the body. 

 The quantity of urea and uric acid in the urine is increased 

 very considerably by salicylic acid, and usually the amount 

 of urine itself. It is made aseptic by the escaping salicylic 

 acid, or in the case of salol, by both carbolic and salicylic 

 acids. The urine of animals taking salicylic acid may be 

 rendered green by indican and pyrocatechin, formed through 

 the action of pancreatic juice, and takes on a purple color 

 with ferric chloride. 



Toxicology. — In man, continued large doses give rise to 

 delirium, vomiting, depression of the circulation, epistaxis, 

 hsematuria, and retinal haemorrhages. The herbivora are not 

 easily affected by large doses of salicylic acid or salicylates, 

 but dogs exhibit nausea and vomiting, accelerated , respira- 

 tion, irregular pulse, loss of muscular strength, staggering 

 gait, stupor, and, if death occurs, it is preceded by slow 

 breathing, dilated pupils, dyspnea, and convulsions due to 



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