146 INORGANIC AGENTS 



of the air passages. Ammonia stimulates the respiratory 

 centre "vvhen it is injected into the blood. Given under the 

 skin in lethal doses, ammonia causes death by paralysis of 

 the respiratory centres. 



Circulation. — It is probable that ammonia only acts re- 

 flexly to stimulate the heart through irritation of the stom- 

 ach, when it is ingested. If given intravenously or subcu- 

 taneously, ammonia stimulates directly the heart muscle, 

 and probably the accelerator and vasomotor centres, making 

 the cardiac pulsations stronger and quicker and increasing 

 vascular tension. Earely the vagus centre is stimulated and 

 the heart's action slowed. Lethal doses paralyze the cardiac 

 muscle. Ammonia differs from alcohol in being more evan- 

 escent as a stimulant, in not affecting the brain nor meta- 

 bolism, and in not acting as a food. 



Blood. — The normal blood contains ammonia, which is 

 supposed to aid in maintaining its fluidity. The action on the 

 blood is unknown. Ammonia is thought to prevent coagu- 

 lation of blood within the vessels in conditions favorable to 

 thrombosis. 



Nervous System. — An intravenous injection of a lethal 

 dose of ammonia occasions tetanic convulsions in animals, 

 owing to stimulation of the reflex and motor functions of the 

 cord. Medicinal doses excite the spinal reflex and motor 

 centres. Where ammonia is applied directly to nerve tissue 

 it excites' in dilute solution, but paralyzes functional activity 

 in concentration. The brain is unaffected by the therapeutic 

 administration of ammonia. 



Elimination. — Ammonia combines with acid in the 

 stomach and is absorbed into the blood. Ammonia and its car- 

 bonate are oxidized in the body and transformed into \irea, 

 in which form ammonia compounds escape in the urine. 

 Urea being the most active diuretic there is some augmented 

 flow. The urine is, however, not alkalized as by the salts of 

 the other alkaline metals. 



Summary. — Heart and respiratory stimulant and ant- 

 acid. Externally, rubefacient, vesicant, and escharotic. 



TJs6s. — The indications for ammonia are closely in ac- 

 cord with its physiological actions. 



Externally. — It is frequently used in stimulating lini- 



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