5i 8 BIOLOGICAL PHYSICS 



Oxygen, being held in mere suspension by the other 

 elements of the atmosphere, is immediately available for 

 the chemical phenomena of metabolism, without the 

 necessity of antecedent chemical disunion, and so can 

 effect, from the moment of its introduction into the blood 

 stream, those changes in its chemico-physiological con- 

 dition constituting the transmutation of the venous into 

 arterial blood, with all the subsequent changes involved 

 in the subsequent re-conversion of the arterial into 

 venous blood. Whether the other ingredients of atmos- 

 pheric air subserve any purpose in the effecting of aeration 

 of the blood, and the performance of metabolic function, 

 is yet unproved ; but the inference is at least legitimate 

 that they are not altogether devoid of physiological or 

 chemical influence in the complex processes of haemo- 

 genesis and nutrition, as, in all great and small natural 

 processes, no element in their performance is without 

 its effect, negative or positive, and, therefore, we may 

 believe that here we have to do with no exception to the 

 rule ; hence, science must still pursue her enquiries into this 

 comparative terra incognita of chemico-physiology. 



As we have said, the physical element of water, and the 

 chemical element of oxygen, pursue analogous courses in 

 the process of nutrition the former dissolving or sus- 

 pending, and the latter chemically combining with, the 

 elements of the nutritive pabulum submitted to the 

 exhausted tissues, each combining with the other in 

 carrying out the complex details of the materio-dynamic 

 process of tissue waste and repair. 



Water thus constitutes the circulating medium in 

 which the supply of fresh nutritive materials are con- 

 veyed to the worn and wasted tissues, while oxygen 

 constitutes the intrinsic element of chemical currency by 

 which the problems of exchange are effected in the 

 disposal of new for old tissue constituents. 



In the cryptic process of metabolism we are yet far 

 from knowing exactly what takes place, and how its 

 details, chemical and physiological, are effected, as well 

 as what constitutes the line of normal procedure or 

 absolutely healthy action, and what may be looked upon 

 as an altogether pathological departure from the standard 



