310 INOEGANIC AGENTS 



nitrite and nitroglycerin are essentially the same. Spirit 

 of nitrous ether should contain i per cent, of ethyl nitrite. 

 Analysis of 68 samples taken at random from drug stores, 

 resulted in showing that a teaspoonful of the best specimen 

 contained as much ethyl nitrite as a pint of the worst, with 

 all manner of variations between these extremes. To be 

 of value as a nitrite, sweet spirit of nitre should be freshly 

 prepared by a reliable chemist. 



Circulation. — The important action of the nitrites 

 centres upon the heart and blood vessels. The arteries and 

 veins all over the body (but particidarly of the head and 

 belly) become relaxed and blood tension is lowered by the 

 nitrites. This action is no doubt perif)heral, and is due to 

 direct depression of the unstriated muscle of the vessel 

 walls. The heart beats more rapidly in consequence of the 

 lessened vascular resistance and direct depression of the in- 

 hibitory centre and because a diminished blood pressure 

 indirectly depresses the vagus centre and often stimulates the 

 accelerator. The arterioles being dilated in the heart, as 

 elsewhere, there follows an increased cardiac blood supply, 

 nutrition and force. It is probable that the nitrates also 

 stimulate the cardiac ganglia, and increase the force as well 

 as the rapidity of the heart. This is shown by the fact that 

 in small doses blood pressure is raised by the nitrates, de- 

 spite the vascular dilatation. Poisonous doses depress the 

 heart muscle and the pulse becomes slow and weak. 



Nervous System. — The nitrites depress the spinal motor 

 centres. This is more marked in the frog than mammals, 

 however. Neither the motor nor sensory nerves nor cere- 

 brum appear to be influenced by medicinal doses of nitrites. 

 Keflex excitability ■ is lessened. 



Muscles. — Amyl nitrite paralyzes both unstriated and 

 striated muscular tissue when applied locally; and the ni- 

 trites, when administered internally, relieve spasm of mus- 

 cular tissue by their depressing action upon the motor nerves 

 and muscles. 



Kidneys. — ISTitrites often increase the flow of urine by 

 widening the renal arteries supplying the glomerules. But 

 the general lowering of blood pressure may prevent an in- 

 crease of local pressure in the kidney, when urinary secre- 

 tion will be diminished. 



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