220 



PEOF. G. SIMS WOODHEAD. M.D., 



the conditions of life vary so greatly in different planets that 

 only extremely simple forms could have been transferred from 

 one planet to another with any real chance of surWval, and 

 only such simple forms could act as a stem from which the two 

 branches leading up to the higher plants on the one hand, and 

 the animals on the other, could develop. 



^"Sliether life was generated in this globe of ours, or whether 

 it arose in some other planet, is, after all, a matter of com- 

 paratively little import as regards the main question at issue. 

 Should we be able to prove that living matter has come to us 

 from the nearest star on which life existed preWously, it cai'ries 

 us but one step further back, and helps us little towards the 

 solution of the main question. A? Professor Schafer pointed 

 out in his address before the British Association at Dundee. 

 Fischer and his school are gradually proving by synthetic 

 methods that even the constitution of the proteins is no longer 

 an altogether unsolved secret to the chemist. Our knowledge of 

 protoplasm and its chemical constitution is gradually expanding, 

 and at the same time evidence is being obtained, mostly from 

 pathological investigations, that there are forms of li^ing matter 

 so minute that they do not come within the direct range of our 

 most powerful microscopes, and that though they are not kept 

 back by our finest filters, they have the power of multiplying 

 and of inducing diseases during which the most profound 

 changes take place in the animal body. These organisms are 

 liighly specialized in their functions, and probably require 

 special surroundings and conditions for their existence ; never- 

 theless, they are l3eyond our ken, we can see nothing but their 

 shadows, they are impondemble, and we have no means of 

 measuring them in any way except by the results they pro- 

 duce. Minute as they are — much smaller than the ordinary 

 cells of plants and animals — we know that they must be 

 complex bodies, coustmcted out of many molecules, and per- 

 vaded by many ions and electrons, and can have developed but 

 with time and opportunity. 



The pathologist engaged in the study of the changes that 

 take place in function and structure during the coui-se of what 

 we speak of as " disease," especially those in connection with 

 the method of attack and defence of the organism, is invariably 

 first attracted by the chemico-physical explanation of the 

 course of events. One of the first results of Pasteui^'s demon- 

 strations of the continuity and specificity of living matter was 

 the increased importance that was attached to the chemical 

 side of vital processes. Living organisms came to be looked 



