IK) OF RESPIRATION. 



an uneasy sensation, which is instinctively removed by another 

 inspiration,, and thus respiration afterwards continues through 

 life. The fact of respiration commencing before the chord is 

 tied, shows that neither the congestion in the aorta, nor the 

 deficiency of chemical changes, is the cause of the first 

 inspiration. 



The elasticity of the lungs is 'not sufficiently great to expel 

 the whole of their air in expiration, Avhence they remain con- 

 stantly in a certain degree of distention, and the course of the 

 blood through them is never completely obstructed by expiration. 



(D) It is now ascertained, that no oxygen is absorbed in ordi- 

 nary respiration, but that what disappears goes entirely to unite 

 with the carbon of the blood and produce carbonic acid, the 

 latter being exactly equal in bulk to the oxygen that disappears, 

 about 27i cubic inches per minute, or 39,534 in 24 hours, 

 according to the experiments of Messrs. Allen and Pepys, a 

 quantity containing about 11 oz. troy of solid carbon, and per- 

 haps about double the average result of most other experiments. 

 Mr. Ellis* contends that the carbon escapes from the vessels 

 and unites with the oxygen externally, and Dr. Prout thinks 

 this opinion corroborated by a fact stated by Orfila/j- that when 

 phosphorus dissolved in oil is injected into the bloodvessels, 

 vapours of phosphorous acid stream from the mouth and nos- 

 trils, which would hardly have occurred if the acid had been 

 formed in the vessels, as it would probably have remained in 

 solution in the blood, not being volatile : the phosphorus was 

 probably excreted from the vessels in minute subdivision, and 

 united with the oxygen of the atmosphere upon coming in con- 

 tact with it, producing phosphorous acid ; and the same may 

 be imagined respecting the carbonic. J Allen and Pepys ob- 

 served that if respiration of the same air was breathed repeatedly, 

 some oxygen was absorbed ; and that if nearly pure oxygen was 



* On Respiration. -f- To.ricologic Generate, 



J Thomson's Annals of Philosophy. 1819. 



