4 PHYSIOLOGY 



and experimental ; the third, descriptive, experimental, and 

 speculative. For the first, direct or indirect observation, i.e. the 

 exact perception of vital phenomena, suffices whether by the 

 normal use of the senses only or by the help of instruments 

 designed to reinforce them. For the second, observation is not 

 enough, experiment also is required, i.e. premeditated observation, 

 in which the external and internal conditions of the living 

 phenomena can be varied. In the third, besides observation and 

 experiment, an energetic criticism is imperative, i.e. the logical 

 elaboration by the physiologist of the collected analytical data, in 

 order to interpret and synthetise them. This, in the majority 

 of cases, resolves itself into the arrangement of vital facts in 

 order of co-existence and succession, or of co-ordination and sub- 

 ordination. 



In the first grade of physiological science we have an accumu- 

 lation of loose facts, more or less unorganised, but adapted to call 

 up a picture of the various and manifold energies of which the 

 living organism is the seat. In the second, we arrive at an 

 ordering and systematisation of the said energies, which enables 

 us more or less clearly to conceive what Galen called the " iisus 

 partium" i.e. the topography of the vital functions. The third 

 aims at harmonising the same energies, in order, by our knowledge 

 of the influences exerted by each element or organ upon 'the 

 other elements or organs of which the body consists, to form an 

 idea as to how that individual unity is built up, which is revealed 

 to us subjectively as the ego, objectively as the complete harmony 

 of functions that characterises the state of perfect health. 



The first and second' grades of physiological science have a 

 positive, immanent value, which time can only develop and per- 

 fect, while the third has seldom more than a hypothetical value, 

 which is for the most part temporary, and therefore varies with 

 time. It follows that facts, if well observed, and experimental 

 data well harvested, are and will for ever be true in the progress 

 of science, while the interpretation of facts, and their logical 

 order, may vary greatly, and even alter fundamentally, with the 

 advent of new data or new discoveries. 



III. In the interpretation of vital phenomena, the physiologist 

 seeks to apply the known laws of physics and chemistry, starting 

 from the obvious position that organised bodies cannot lie beyond 

 the scope of the laws of Nature. The interpretation of these laws 

 is entirely based on the atomistic hypothesis of matter, with its 

 corollary that the indivisible elements of which matter is com- 

 posed are in themselves indestructible and invariable in their 

 fundamental properties, having, i.e., the same specific weight, the 

 same valency or saturation capacity, the same affinity. The 

 energy of which the atoms are the seat may be potential or 

 kinetic. The former is transformed into the latter, and vice versa, 



