20 Effects of Oxygen and other Gases. 



valuable considerations ; and these, however curious the re- 

 searches of chemists have been, and of whatever practical 

 importance, principally belong to the department of the phy- 

 siologist. 



If the poisonous principle, upon which the gases now^ enume- 

 rated act, be inquired into, it may probably be referred to the 

 sedative class of poisons, which operate so quickly and so decid- 

 edly on the centre of the nervous system to the suspension of sen- 

 sibility, and frequently without interfering directly with vital con- 

 tractility. It does not appear that they act until they absolutely 

 reach the brain, and then with variable intensity, according to 

 circumstances casually influencing their effects. But, in my 

 experiments, the constancy of effect was very marked ; and 

 the smaller the animal the quicker was the operation upon the 

 brain, arid the larger, the slower was the effect. So that, when 

 the gases are pure and carefully preserved, no variations occur 

 to render the results doubtful and precarious, and the modifi- 

 cations of the results may be usually anticipated. Although it 

 is not my object at present to indulge in any speculative ideas 

 which may arise out of these experiments — which, in some 

 instances, are confirmed by modern physiologists, who have 

 themselves corrected former errors — yet I cannot avoid the 

 opportunity afforded me, from my facts, of referring to the 

 unscientific method, even now not quite extinct, of attempting 

 reanimation, in cases of suspended sensibility from exposure to 

 certain gases. The inutility and mischief of the treatment al- 

 luded to cannot be too strongly and frequently pointed out ; 

 nor can the plain and simple indications of nature, as deve- 

 loped by experiments, be too fully made manifest, from refer- 

 ence to the principle on which the noxious gases operate upon 

 animal life, and which it is the province of the physiologist to 

 investigate and make known. 



