-i 
1894.] The Scope of Modern Physiology. 479 
morphologist. The current researches and discussions on evo- 
lution, heredity, and other fundamental questions make this 
constantly more evident. Like zoology and botany, each has 
- its special field of labor, its special methods, and its special 
problems; but the fields are constantly overlapping, the one 
learns methods from the other, and the ultimate problems of 
both are the same. 
Let us now draw together the main lines of our thesis. I 
prefer to conceive of physiology as the science of the dynamics 
of living matter. Its tasks for the future seem to comprise the 
following classes of investigations. 
First, the functions of adult organs, tissues and cells in 
plants, Invertebrates and Vertebrates. The greatest interest 
at present appears to center about the phenomena of heredity, 
the central nervous system, and general cell physiology. 
Second, the ontogeny of functions, or embryological physiology. 
Third, the phylogeny of functions. Fourth, the physiology of 
organisms, comprising the mutual relations of organisms to 
each other and to their environment. 
It would be superfluous here to discriminate between the 
opportunities for research offered in these four classes of prob- 
lems. Each covers a wide field of rich promise. Each is 
largely worked—in reality, as we have shown, research in the 
past has been confined almost wholly to the first group. Each 
-will lead the investigator to fundamental problems. 
In considering these tasks it will be perceived that I have 
viewed the organism in two aspects, in its internal and its ex- 
ternal relations. The problems of the first three groups may 
be regarded as belonging to internal physiology, those of the 
fourth to external physiology. Nearly twenty-five years ago, 
ae Haeckel made a similar division into Conservations- and Rela- 
_ lons-Physiologie* Such a classification is convenient and val- 
uable. But it must be remembered that it is artificial, and 
. . Must not be taken as indicating a fundamental distinction 
_ between two sciences. The two are departments of the one 
Science, physiology, and pass the one into the other. For a 
fact that becomes the more striking, the longer one studies the 
| “Senaische Zeitschrift, V, 1870. 
