ACTION OF THE NITRITES 333 



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 

 nitJite, 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 

 particularly of the head, limbs, heart and belly) become relaxed and 

 blood tension is lowered by the nitrites. This action is no doubt peri- 

 pheral, 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 inhibitory centres or 

 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 nitrites slightly 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 nitrites, despite the vascular 

 dilatation. However, the nitrites, as nitroglycerin, are not of practical 

 value as heart stimulants in poisoning (anesthetics) or emergencies, par- 

 ticularly where the vasomotor tone is depressed. The stimulant action 

 on the heart has been much overrated and is practically nil. 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 cerebrum appear to be influenced by medic- 

 inal doses of nitrites. Reflex excitability is lessened. 



Muscles. — ^Anlyl nitrite paralyzes both unstriated and striated mus- 

 cular tissue when applied locally; and the nitrites, when administered 

 internally, relieve spasm of muscular tissue by their depressing action 

 upon the muscles, as of bronchial muscles in asthma. 



Kidneys. — Nitrites often increase the flow of urine by widening the 

 renal arteries supplying the glomerules. But the general lowering of 

 blood pressure may prevent an increase of local pressure in the kidney, 

 when urinary secretion will be diminished. 



Blood. — In poisoning by the nitrites, the oxidizing power of the 

 blood is lost. Both the venous and arterial blood become of a chocolate 

 hue from the conversion of the normal oxy-hemoglobin into meta-hemo- 

 globin. The latter yields up oxygen very sparingly. 



Respiration, — The respiratory movements may be increased both in 

 force and frequency by medicinal doses of nitrites, but paralysis of the 

 respiratory centre and asphyxia occur in fatal poisoning. 



Elimination. — The nitrite group rapidly escape in the urine as 

 nitrites and nitrates of the alkalies. The amyl, of amyl nitrite, is com- 

 pletely oxidized in the body, while nitroglycerin is eliminated in part 

 unchanged in the urine. 



Summary. — The nitrites dilate arterioles, increase the rate of the 



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