J 53 KEPOKT — 1871. 



gested many new applications of it ; but the credit of tlie earliest observa- 

 tions, as I stated at Newcastle, belongs strictly to Professor Guthrie. 



It will be remembered by some that in one of my early papers on nitrite 

 of amyl I pointed out that the effects observed were clearly due to an in- 

 duced paralysis of the vascular system, of the terminal part of that system, 

 and that the heart passed into vehement motion, not, as I at first had thought, 

 because it was excited by the agent, but because the resistance to its action 

 being removed, it ran down like a clock in which the resistance to the 

 spring is broken by the removing of the pendulum or the pallets. I 

 further explained that the seeming over-action produced by the nitrite was 

 in truth no evidence of power or tension of muscle, but that in truth, under 

 the influence of the nitrite, the muscular system is brought into extreme 

 relaxation, so that the substance might be used as a remedy for the relief 

 even of tetanic spasm. These views have been sustained by later observa- 

 tion. It remained, however, still to discover how far the relaxation of ves- 

 sels from nitrite of amyl extended to the fimctious of special oi-gans of the 

 body ; and during the present year I have followed up this line of research 

 in respect to the changes producible by it in the pulmonary organs, the lungs. 

 The study has been most fruitful, and will, I think, as it is foUowed up, open 

 qtiite a new field of accurate and sound observation as to the mode in which 

 many diseases of the lungs take their origin. 



As there may be many here who are not conversant with the nature and 

 properties of nitrite of amyl, I may say briefl}^ in respect to it, that it is an 

 amber- coloured fluid, having the odour of ripe pears, and, although requiring 

 a high temperature for ebullition, volatilizing very readily on exposure to 

 the air. 



When taken into the body nitrite of amyl produces intense flushing of the 

 face, throbbing and sensation of fulness in the head, rapid action of the heart, 

 and in time a sense of breathless exhaustion. In my previous Reports I 

 have entered at length into details of its action, of which the following is a 

 summary. 



The nitrite, though insoluble in water, will enter the body and produce 

 its specific action by any channel of the body, by the cellular tissue, stomach, 

 blood. It produces general muscular paralysis, aff'ecting directly or indirectly 

 all the motor centres. 



It exerts no primary action on the sensory centres, and therefore does not 

 produce anassthesia. 



Its paralyzing action seems first to be directed to the organic nervous 

 centres, by which the vascular tension is reduced. It acts, in fact, after tho 

 manner of an emotional sjiock, leading quickly to paralysis of the minute 

 vessels. 



It prevents oxidation by its presence, and possesses distinct antiseptic 

 powers. It produces a peculiar tarry condition of the blood, but docs not 

 materially impede coagulation. 



It neutralizes the tetanic action of strychnia, and removes tetanic spasm. 



On reviewing these inferences of former years, as thus detailed, I see no 

 occasion to change one of them ; indeed I believe they have, on the whole, 

 all been confirmed by other observers. The admirable experiments of Dr. 

 Brunton on the action of the nitrite on vascular tension call for special re- 

 cognition. There is, however, one observation in my Ileport of 1864 I would 

 like to correct. f?pcaking at that time of the action of the nitrite on the 

 muscles, I remarked that it first excites the muscular system, and then para- 

 lyzes it. I am in doubt now whether the muscular excitement of which I 



