FREE BOOKS

Author's List




PREV.   NEXT  
|<   315   316   317   318   319   320   321   322   323   324   325   326   327   328   329   330   331   332   333   334   335   336   337   338   339  
340   341   342   343   344   345   346   >>  
ill, therefore, be a fit period to conclude our present conversation. What further remarks we have to make on the animal economy shall be reserved for our next interview. CONVERSATION XXVI. ON ANIMAL HEAT; AND ON VARIOUS ANIMAL PRODUCTS. EMILY. Since our last interview, I have been thinking much of the theory of respiration; and I cannot help being struck with the resemblance which it appears to bear to the process of combustion. For in respiration, as in most cases of combustion, the air suffers a change, and a portion of its oxygen combines with carbon, producing carbonic acid gas. MRS. B. I am much pleased that this idea has occurred to you: these two processes appear so very analogous, that it has been supposed that a kind of combustion actually takes place in the lungs; not of the blood, but of the superfluous carbon which the oxygen attracts from it. CAROLINE. A combustion in our lungs! that is a curious idea indeed! But, Mrs. B., how can you call the action of the air on the blood in the lungs combustion, when neither light nor heat are produced by it? EMILY. I was going to make the same objection. --Yet I do not conceive how the oxygen can combine with the carbon, and produce carbonic acid, without disengaging heat? MRS. B. The fact is, that heat is disengaged.* Whether any light be evolved, I cannot pretend to determine; but that heat is produced in considerable and very sensible quantities is certain, and this is the principal, if not the only source of ANIMAL HEAT. [Footnote *: It has been calculated that the heat produced by respiration in 12 hours, in the lungs of a healthy person, is such as would melt about 100 pounds of ice.] EMILY. How wonderful! that the very process which purifies and elaborates the blood, should afford an inexhaustible supply of internal heat? MRS. B. This is the theory of animal heat in its original simplicity, such nearly as it was first proposed by Black and Lavoisier. It was equally clear and ingenious; and was at first generally adopted. But it was objected, on second consideration, that if the whole of the animal heat was evolved in the lungs, it would necessarily be much less in the extremities of the body than immediately at its source; which is not found to be the case. This objection, however, which was by no means frivolous, is now satisfactorily removed by the following consideration:-- Venous blood has been fo
PREV.   NEXT  
|<   315   316   317   318   319   320   321   322   323   324   325   326   327   328   329   330   331   332   333   334   335   336   337   338   339  
340   341   342   343   344   345   346   >>  



Top keywords:

combustion

 

ANIMAL

 
produced
 

animal

 

respiration

 
oxygen
 

carbon

 

process

 

carbonic

 

theory


interview

 

evolved

 
objection
 

consideration

 
source
 
pretend
 
pounds
 

Whether

 

determine

 

disengaged


calculated

 

healthy

 
person
 

quantities

 

Footnote

 

principal

 
considerable
 

original

 

immediately

 

extremities


necessarily

 

removed

 

Venous

 

satisfactorily

 

frivolous

 

objected

 

adopted

 
afford
 

inexhaustible

 

supply


elaborates

 

wonderful

 
purifies
 
internal
 

equally

 

ingenious

 

generally

 
Lavoisier
 

simplicity

 

proposed