28 REPORT— 1841. 



Inhaled bj' tlie breath, it is well known to produce serious and alarming 

 symptoms, varying as the gas may be more or less diluted. The following 

 experiments show its effects when injected into the vessels. 



Experiment I. — To shotv the Effect of Carbonic Acid injected into the Veins. 



Two fluid ounces (by measure) of this gas, prepared by the action of di- 

 luted hydrochloric acid upon chalk, were collected over water, and thrown 

 slowly, by a syringe, into the external saphsena vein of a strong dog. Almost 

 immediately afterwards the animal exhibited signs of uneasiness, uttered 

 cries of distress, became convulsed, lost its consciousness, and appeared to be 

 dying ; it felt, however, the stimulus of cold water when thrown upon it, and 

 quickly recovered upon being removed into the fresh air. 



It thus is capable of producing a powerful impression on the system, when 

 thrown into the veins even in a small quantity. Still more marked results 

 ensued when it was introduced into an artery, as was shown in the next ex- 

 periment. 



Experiment II. — To show the Effects of Carbonic Acid when thrown into 



the Carotid Artery. 



The left external carotid artery M^as exposed in the same dog, and a small 

 tube was introduced into it, a ligature having previously been applied to 

 prevent hemorrhage: a fluid ounce and a half (by measure) of carbonic acid 

 was then thrown in. This was done gently, but it was necessary to discon- 

 tinue the experiment, in consequence of the animal becoming convulsed and 

 foaming at the mouth. After forty seconds it seemed to recover ; but again 

 relapsed, lost all consciousness and power of movement, was quite insensible, 

 and lay as if dead upon the floor. At intervals of a few minutes it was seized 

 with attacks of violent spasms. This alternation of stupor and convulsions 

 continued for four hours, when the animal regained its senses, the power of 

 its limbs, and appeared afterwards to suffer no inconvenience. 



M. Nysten considers that the eff'ects witnessed on throwing carbonic acid 

 into the vessels arise from the distension of the right side of the heart ; this 

 seems, however, questionable in the experiment just detailed, as the gas was in- 

 jected slowly in a direction from the heart, and produced other symptoms 

 than those described as arising from the simple admixture of air with venous 

 blood*. This eminent experimentalist certainly errs in considering that 

 carbonic acid is not itself intrinsically poisonous. It cannot be necessary to 

 pause in order to refute this idea, but it is worth while to mention the diver- 

 sity in its effects : some speak of experiencing a lively sensation of pleasure 

 on respiring it ; others, of the sensation of a gentle heat and perspiration ; 

 and Sir Humphry Davy said he could answer, from his own experience, 

 that no pain precedes the insensibility occasioned by breathing gases un- 

 fitted for supporting life-j-. In general, however, vertigo, head-ache, accele- 

 rated pulse, hurried breathing, palpitation of the heart, tendency to sleep, 

 ending in complete loss of consciousness, with convulsions, mark its effects 

 during life ; whilst retention of the warmth of the body, flexibility of the 

 limbs, fluidity and blackness of the blood, characterise after death the bodies 

 of those poisoned by this gas. 



If we now turn to those diseases, the leading symptoms of which bear resem- 

 blance to the effects of carbonic acid, we find them to be such as prevent the 

 proper arterialization of the blood, emphysema of the lungs, diseases of the 

 heart; or, to be brief, all such as impede respiration, in which cases we find 

 hebetude of mind, torpor of body, inclination to doze, spasmodic respiratory 



* Mayo, Phys., p. 72. t Salmonia, p. 112. 



