14 EEPORT— 1893. 



of cell-development and growth, and so, by making pathology a part of 

 physiology, secured its subsequent progress and'its influence on practical 

 medicine. Similarly in physiology, the achievements of those years led 

 on without any interruption or drawback to those of the following gene- 

 ration ; while in general biology, the revolution in the mode of regarding 

 the internal processes of the animal or plant organism which resulted 

 from these achievements, prepared the way for the acceptance of the still 

 greater revolution which the Darwinian epoch brought about in the views 

 entertained by naturalists of the relations of plants and animals to each 

 other and to their surroundings. 



It has been said that every science of observation begins by going out 

 botanising, by which, I suppose, is meant that collecting and recording 

 observations is the first thing to be done in entering on a new field of 

 inquiry. The remark would scarcely be true of physiology, even at the 

 ■earliest stage of its development, for the most elementary of its facts 

 could scarcely be picked up as one gathers flowers in a wood. Each of 

 the processes which go to make up the complex of life requires separate 

 investigation, and in each case the investigation must consist in first 

 splitting up the process into its constituent phenomena, and then deter- 

 mining their relation to each other, to the process of which they form 

 part, and to the conditions under which they manifest themselves. It 

 will, I think, be found that even in the simplest inquiry into the nature of 

 vital processes some such order as this is followed. Thus, for example, 

 if muscular contraction be the subject on which we seek information, 

 it is obvious that, in order to measure its duration, the mechanical work 

 it accomplishes, the heat wasted in doing it, the electro-motive forces 

 which it develops, and the changes of form associated with these phe- 

 nomena, special modes of observation must be used for each of them, 

 that each measurement must be in the first instance separately made, 

 under special conditions, and by methods specially adapted to the 

 required purpose. In the synthetic part of the inquiry the guidance of 

 experiment must again be sought for the purpose of discriminating 

 between apparent and real causes, and of determining the order in which 

 the phenomena occur. Even the simplest experimental investigations 

 of vital processes are beset with difficulties. For, in addition to the 

 extreme complexity of the phenomena to be examined and the un- 

 certainties which arise from the relative inconstancy of the conditions 

 of all that goes on in the living organism, there is this additional draw- 

 back, that, whereas in the exact sciences experiment is guided by well- 

 ascertained laws, here the only principle of universal application is that 

 of adaptation, and that even this cannot, like a law of physics, be taken 

 as a basis for deductions, but only as a summary expression of that 

 relation between external exciting causes and the reactions to which 

 they give rise, which, in accordance with Treviranus' definition, is the 

 essentia] character of vital activity. 



