PHYSIOLOGICAL ACTION OF ORGANIC CHEMICAL COMPOUNDS. IGl 



onward movements. In tlie veins, too, there were now and then short move- 

 ments, fii-st as of impulse towards the heart, and then of retreat backwards ; 

 these movements in the veins were succeeded invariably by an increased and 

 more perfect action of the arteries. During this state the capillaries may bo 

 said to have become almost indistinct, that is to say, no movement of cor- 

 puscles through them, into tho veins, indicated their course ; as channels they 

 were left empty and transparent, and the return of the corpuscular current 

 through them was at all times proof of the speedy return of the activity 

 of life. 



The changes named above were common to the action of all the narcotics 

 named ; but there were some striking changes peculiar to the substances 

 themselves to which I must refer. The peculiarities were traceable, as it 

 seems to me, to the weight, the solubility, and the chemical composition of 

 the substance that was employed to produce the narcotic state. 



When the substance was very light, of low boiling-point, and insoluble, 

 the effect of arrest of the circulation was most rapidly developed, and at the 

 same time was most rapidly removed. Thus hydramyle, the lightest, the first 

 to boil on elevation of temperature, and the most insoluble, produced tho 

 quickest arrest of the venous current ; but from its influence the animal was 

 equally quick to recover, the general signs of recovery being secondary to 

 the local return of the circulation. 



When the substance was light and of low boiling-point, but comparatively 

 soluble in blood, the time required to produce the slowing of the venous cir- 

 culation was prolonged after the insensibility of the animal was complete ; 

 after even respiration had stopped, the extreme changes in the circulation 

 were slowly developed ; and although the insensibility might be deep and 

 continuous, like to death itself, the actual temporary arrest of the arterial 

 current was imperfectly pronounced. Absolute ether, which has a very low 

 specific weight (720) and a very low boiling-point (94° F.), but which is solu- 

 ble in blood to the extent of not less than eleven parts in the hundred, pro- 

 duced perfectly all the effects immediately named above. When the substance 

 inhaled was comparatively heavier, of a higher boUing-point, insoluble, and 

 contained as one of its elements an irritant, there was introduced a new 

 phase, that is to say, the arterial vessels, as the animal came under the in- 

 fluence of the narcotic, were reduced in calibre. The changes of the circula- 

 tion in this case were first marked in the retardation of the blood through 

 the veins, then the vein increased in diameter, and there were signs of 

 regurgitation of its blood; these indications were followed by what may 

 be called irregular movements in the capillaries, and by reduction of calibre 

 of the arteries. It was observed, nevertheless, that the narrowing of tho 

 arterial vessels, though well marked, was never so extreme as to prevent mo- 

 tion of blood in them ; that is to say, the degree of arterial contraction was 

 limited. I consider this to be due to the circumstance that the animal had 

 always ceased to breathe, and the further absorption of the narcotic vapour 

 had consequently also ceased, by the time that the action of the vapour upon 

 the arterial vessels was developed. 



During the period when the size of the arterial vessel was reduced, the 

 motion of the blood in the capillary vessels fed by the arterial supply was 

 modified; the blood flowing through the capillaiy channels moved less 

 steadily, and was forced, if I may so express the fact, in pushes, as if there 

 were intervals of relaxation of the arterial vessels during which the resis- 

 tance to the impelling power of the heart slightly and slowly yielded. 

 After a time the circulation of the blood through the artery became slo^ver, 



JL871. M 



