16 president's address. 



i.e. , that the physical laws of the diffusion of gases do not hold in this 

 case. There is a noteworthy difference in the view of the same 

 facts of gaseous respiratory exchange taken by Martin. In his view 

 the results of experiments show that "the exchange of gas between 

 the blood plasma and the alveolar air is regulated to some extent 

 according to the law of partial pressures." And, with regard to 

 the above-mentioned strikingly anomalous behaviour of the respi- 

 ratory oxygen (first announced by Bohr, and since confirmed by 

 the work of Haldane and Lorrain Smith), Martin cautiously 

 remarks that this fact " cannot be explained by diffusion across 

 a membrane, with which one is so far acquainted in physical 

 experiments." But it is to be observed that this inadequacy of 

 physical explanation suggests to him, not a break in the continuity 

 of mechanical theory as applicable to the phenomena under con- 

 sideration, but simply a new physical hypothesis as to the material 

 structure of a membrane which should allow of such novel 

 behaviour. And so on, wherever the known laws of physics and 

 chemistry seem incapable of accounting for the activities mani- 

 fested in living matter, the question for Martin seems ever to be 

 " if this be not a case of the operation of known mechanism, what 

 is the actual and genuine mechanism underlying it ; if the 

 originally supposed mechanism is not the true cause of the opera 

 tion, what is the real and actual antecedent cause 1" And to me 

 this appears to be the only genuinely scientific question, the only 

 kind of question answerable by means of experimental scientific 

 procedure. 



The question may be brought into relief by the use of a familiar 

 quotation from Clerk Maxwell — " Now one material system can 

 differ from another only in the configuration and motion which 

 it has at a given instant. To explain differences of function and 

 development of a germ without assuming difference of structure 

 is, therefore, to admit that the properties of a germ are not those 

 of a purely material system." Here, of course, it is the one 

 physiological process of develoj)ment which is in view. For the 

 present purpose we might write " living cell " in place of "germ" 

 or germ-cell. On the lines of Clerk Maxwell's formula, the 



