INFLUENCE OF TEMPERATURE. 555 



that after immersion for some time in a cold 

 bath, the surface of the body assumes a purple 

 hue, as when exposed to a very cold atmosphere ; 

 but if transferred to a warm bath, the skin 

 changes to a bright scarlet colour. It is, there- 

 fore, obvious that the arterial blood of the cuta- 

 neous capillaries is venalized by the abstraction 

 of caloric alone, without any loss of ponderable 

 matter, and again arterialized without the ad- 

 dition of oxygen. Again, if it were established 

 that venous blood is brightened by uniting with 

 oxygen, and darkened by parting with carbonic 

 acid, the injection of oxygen into the veins will 

 not support life when the chemical function of 

 the lungs is arrested, any more than nitrogen, 

 hydrogen, or any other description of ponderable 

 matter. As a further proof that oxygen is not 

 the agent by which the fluids are formed, and 

 converted into the various tissues by vital affi- 

 nity, it has no access to the germ of the foetus, 

 which is nourished and lives before any commu- 

 nication is established with the blood of the 

 mother by means of the placenta. 



From all the foregoing facts we are authorized 

 to conclude, 1. that during the passage of dark 

 venous blood through the lungs, it gives off va- 

 riable proportions of carbon and hydrogen, that 

 unite chemically with atmospheric oxygen to 

 form carbonic acid and water, as in ordinary 

 combustion, by which it acquires an addition 

 of caloric, with a bright florid hue; and 2. that 



