CHAPTER IX 



THE WAYS OF BREATHING 

 (RESPIRATORY CONVERGENCE) 



THE factors which combine to produce a structural 

 or organic unit in the animal body which will be 

 fixed by inheritance are inconceivably complex. 

 Nevertheless, we have seen that essentially the 

 same combination can be repeated independently 

 in different cases. The present state of know- 

 ledge justifies the provisional assertion that the 

 higher combination which leads to the establish- 

 ment of an animal form possessing the essential 

 component elements of a definite morphological 

 type, cannot be repeated. The theory of con- 

 vergence is therefore not calculated to precipitate 

 us into morphological chaos, howsoever startling 

 its manifestations may be. 



A great deal might be written upon the large 

 subject of respiratory convergence, but I will 

 touch upon it briefly. Respiration is one of 

 the primary properties of living matter, and the 

 general principle which governs the mechanism 

 of respiration, namely, the diffusion of gases 

 (oxygen and carbon dioxide) through moist 

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