226? RESPIRATION, 



from the brain, it is by the brain being unable to continue respir- 

 ation. 



Still the circulation of venous blood excites in some degree 

 for a time, and is better than no circulation ; for Dr. Edwards 

 placed some frogs, toads, and salamanders with their hearts en- 

 tire, and others deprived of their hearts, in water deprived of air- 

 Those with hearts survived the longest, occasionally twenty hours 

 longer than the others. 11 It is worth remembering, as Dr. Stevens 

 has pointed out, that blood may be black from the presence of 

 carbonic acid, &c. or from the absence of saline matter. 



Venous blood both abounds in carbonic acid and is deficient in 

 oxygen. The state of combination of the oxygen abounding in 

 arterial blood, and of the carbonic acid abounding in the venous y 

 are unknown. As the blood is florid until it reaches the minutest 

 vessels, we presume that in them the oxygen disappears, and the 

 carbonic acid is produced. The oxygen is thought to meet with 

 carbon there, and with it form the carbonic acid. Dr. Prout con- 

 ceives that the carbon is derived from the albumen, when albumin- 

 ous matters are converted into gelatine. This substance, which is 

 not found in the blood nor in any glandular secretion, enters into 

 the structure of every part, and especially of the skin, which is 

 little else. Now this contains three or four per cent, less carbon 

 than albumen. In nutritk>n> therefore, albuminous substances 

 very extensively support a reducing process, lose their carbon, 

 to become gelatinous, and as this process must occur in . the 

 minutest vessels, their blood is charged with carbon, which, how- 

 ever, instantly finds oxygen (probably in solution in the water of 

 the blood), and unites with it into carbonic acid. 1 It is thus that 

 respiration assists assimilation, and not by discharging carbon 

 from the chyle, as many have imagined. They forget that more 

 carbonic acid is not found after every meal, nor less during fast- 

 ing, till this proceeds to the length of debility : and that many 

 animals sleep after feeding, yet in sleep less is produced. 



Some suppose that respiration is very instrumental in prevent- 

 i ng the putrefaction of the living body ; and this by carrying off 

 its carbon, the substance which, in the spontaneous decomposi- 

 tion of animals, is the first rejected, and unites with the oxygen? 

 of the atmosphere ; and, indeed, Spallanzani found, that the dead 



h 1. c. P. 1. c. i. sect. 2. 



' Bridgewater Treatise, pp. 519. 524. sq. 535. sq* 



