AveustT 9, 1918] 
plainly visible in a dividing cell under the 
microscope, attention was naturally focused 
upon them. However, even if any one suc- 
ceeded in connecting up the transmission 
of some particular character to the off- 
spring with some peculiar form of one of 
the chromosomes we still had the question 
of why that particular form was connected 
with that particular character. Thus 
little was accomplished so far as the funda- 
mental problem was concerned. Although 
much knowledge was gained by investiga- 
tions of this sort, they still furnished no 
means of direct attack upon the funda- 
mental problem. 
Investigations of the sort just mentioned 
illustrate the first fundamental defect of 
all corpuscular theories, considered as a 
means of advancing our knowledge of biol- 
ogy, viz., the corpuscles are hypothetical 
and thus merely serve to put biological 
problems beyond the reach of scientific in- 
vestigation. 
A second defect of corpuscular theories 
is that they provide no adequate mechan- 
ism for the correlation of the various or- 
gans making up a complex organism. 
Means of securing dominance of one part 
and subordination of another are lacking. 
With the advance of knowledge of 
physics and chemistry and the growing 
interest in experimental plant physiology, 
the point of view in regard to plant func- 
tions shifted and we were chiefly concerned 
for a time with what may be called the 
chemical point of view in considering the 
phenomena involved in the activities of liv- 
ing organisms. It is of course, evident that 
chemical reactions play a large part in the 
life processes. It is also well known that 
life is closely associated with the substance 
which we call proteins. This gave rise to 
the idea that certain complex protein mole- 
cules are the ‘‘producers of life.’’ 
Though the molecule itself according to 
SCIENCE 
127 
this conception is not alive, its constitution 
is the basis of life and life results from the 
chemical transformations which its labil- 
ity makes possible. The living substance, 
then, says the explanation of life, is a sub- 
stance in which some of the labile mole- 
cules are continually undergoing transfor- 
mation. Life itself would then consist in 
chemical change, not merely in chemical 
constitution. Death must then be regarded 
as a change from lability to stability. The 
dead proteins, which the chemist might 
analyze could not of course, show the prop- 
erties of the living substance, and the 
fundamental problems of life were thus 
again placed outside the realm of experi- 
mental science. 
About 1900 questions began to be heard 
as to the existence of a ‘‘living substance”’ 
of more or less definite chemical structure. 
We are indebted largely to Héber’s book 
published in 1911 for crystallizing our 
ideas as to the hopelessness of the purely 
chemical point of view and pointing the 
way to the physico-chemical, for starting 
us away from the idea that protoplasm is 
merely a complex chemical substance, 
toward the conception of protoplasm as 
composed of many chemical substances ex- 
isting as a complex physical system. This 
assuming a colloid substratum for the or- 
ganism, is the physico-chemical theory of 
life which represents the prevailing point 
of view in the biology of to-day. 
This leads us to look upon the plant as a 
living physical system, receiving energy 
from its environment and doing work that 
is more or less useful to itself and to man- 
kind. It points the way to a definite pro- 
gram for work and is then a source of 
gratification to the modern experimental 
botanist. 
‘“‘The situation at present,’’ says Dr. 
Briggs,® ‘‘may perhaps be fairly summar- 
8 Jour. Wash. Acad. Sci., 7: 89, 1917. 
