REGULATION OF BREATHING 3 



that we must look to a more thorough and direct 

 interpretation.^ 



Breathing is a form of physiological activity which 

 goes on whether we are conscious of it or not. Only 

 by a great effort can we suspend it for 30 or 40 sec- 

 onds, and any hindrance to breathing is violently 

 resisted. Although in the seventeenth century Mayow 

 came very near to discovering the chemical changes 

 in air during breathing, it was not till the latter half 

 of the eighteenth century that these changes were 

 understood. Black found that what we now call 

 carbon dioxide is given off in breathing, and Priestley 

 found that what we now call oxygen disappears as 

 such. Lavoisier put these and many other facts 

 together, and showed that just as in ordinary com- 

 bustion of carbonaceous material, so in connection 

 with respiration, oxygen combines with carbon and 

 hydrogen to form carbon dioxide and water, and to 

 liberate heat. Hence breathing is a process in which 

 the essential factors are the conveyance of oxygen into 

 the body, and the removal from it of carbon dioxide. 

 Breathing can thus be compared to the supply of air 

 to a fire and the carrying off by the air of the products 

 of combustion. 



Subsequent investigation showed that the oxidation 



'^ It has been suggested to me that if a convenient label 

 is needed for the doctrine upheld in these lectures the word 

 "organicism" might be employed. This word was formerly 

 used in connection with the somewhat similar teaching of 

 such men as Bichat, von Baer, and Claude Bernard. Cf. 

 G. Delage, L'Heredite, Paris, 1903, p. 435. 



