THE RELATION OF THE HEAllT-BEAT TO ELECTKOLYTES. 189 



agencies we have named is to be explained in part by the fact that 



their membranes liave been bathed for years before the experiment in 



solutions of slightly different P + . 



H 



There are striking differciices in the relations of the hearts of different 

 Sjpecies of animals to hydrogen ion concentration and to polyvalent ions: 

 these correspond exactly to differences found in the effects of these ions on 

 the ionic permeability of different colloidal materials. A mechanistn is 

 thus suggested which explains how differences in the chemical constitution 

 of a tissue component may cause differences in the physiological behaviour 

 of the living tissue. 



I venture to hope that these fragmentary remarks will make it 

 apparent that a field of research lies open here, containing treasure 

 not alone for the physiologist who desires to elucidate the mechanisms 

 by which vital processes are wrought in the individual, but also for the 

 zoologist, who in looking for clues of genetic affinities has learnt 

 the limitations of pure morphology and the truth of the axiom of 

 physiology that by studying what a cell can do we shall best learn 

 what it is. 



For the furtherance of the science of Comparative Physiology the 

 co-operation of morphologists and physiologists with physical, organic, 

 analytical, and colloid chemists is necessary. This country is not lack- 

 ing in any of these. The study of the science can be carried on best 

 where the greatest variety of animals, living and in good condition, 

 can be provided. This condition is most perfectly fulfilled at a marine 

 station. 



At Plymouth the fauna is rich, and the facilities provided in the 

 Laboratory for keeping animals in condition for physiological experi- 

 ment are admirable. It is earnestly to be wished that more workers 

 in tins country w^ould interest themselves in a branch of zoology 

 and of physiology pregnant with interest for both sciences, and 

 that their efforts might secure for the Plymouth Laboratoiy per- 

 manent accommodation and equipment for physiological work, on 

 a scale approaching that provided by marine stations in other 

 countries. 



In conclusion, I would express my warmest thanks to the Director 

 and Staff of the Laboratory of the Marine Biological Association at 

 Plymouth for much valuable assistance and advice.* 



September, 1911. 



* I am indebted to Professor Stanley Gardiner for tlie use of a University Table at the 

 Plymouth Laboratory during July, August, and part of September. 



The expenses of the researches were defrayed in jiart l)y a grant from tlie Government 

 Grant Committee of the Eoyal Society. 



