upon the Animal System, 11 



tracting long before the heart ceases to act with vigour, and to 

 urge the blood through the vessels. When we refer to these 

 phenomena, and find, also, that the renewal of an atmospheric 

 circulation of air through the lungs is capable of completely 

 restoring animation, we appear to be presented with a train of 

 circumstances strikingly analogous to those which accompany 

 the absorption of certain poisons into the blood. 



The facts, of which I do not find mention made elsewhere, 

 and which induce this analogous assumption, are the pheno- 

 mena described as arising during the respiration of oxygen : — 

 such ^s — the universal appearance of arterial blood; the gra^ 

 dual cessation of sensibility and voluntary motion ; the long- 

 continued breathing only by a slow and feeble action of the 

 diaphragm ; the full continuance of the heart's pulsations, cir^ 

 culating nothing but arterial bloody after the diaphragm has 

 become still ; the restoration of sensibility and voluntary power 

 by atmospheric inflation ; and the maintenance of animal heat 

 within the body during the immersion in oxygen. 



These appear to me to be circumstances well worthy of con- 

 sideration, and necessary to be taken into account, when the in- 

 fluence of pure oxygen upon the animal functions is the object 

 of our inquiry. And, in reference to these circumstances de- 

 tailed, perhaps the following positions may be deemed satisfac- 

 torily established — some of which are corroborated by the 

 experience of others. 



1. Animals immersed in equal quantities of atmospheric air 

 and of pure oxygen, separately, live during different periods ; 

 those in the former dying sooner than those in the latter air. 



2. The gas, remaining after atmospheric respiration, contains 

 carbonic acid in excess, sufficient instantly to extinguish a 

 lighted taper, and to destroy animal life in a few seconds. 



3. The gas remaining, after the respiration of pure oxygen, 

 re-illuminates a blown-out taper, and sustains animal life, during 

 variable periods, as in the first instance of immersion. 



4. The gas of pure oxygen is not much deteriorated by the 

 respiration of animals; while that of the atmospheric compound 

 is rendered wholly unfit to sustain life and flame. 



5. The tendency of an excess of oxygen is to increase the 

 action of the pulmonic and aortic circulation, in the first in- 



