646 
mained for Heidenhain to demonstrate a 
rise of temperature amounting to 0.003— 
0.005°C. with each individual contraction. 
He discovered the fact that the amount of 
heat evolved by a muscle in contraction in- 
creases with its tension ; and in the demon- 
stration that a muscle which contracts 
without doing external work gives off more 
heat than does the working muscle on con- 
traction, the principle of the conservation 
of energy was illustrated by a significant 
experiment. 
To the student of physiology the muscle 
studies briefly referred to may seem to bear 
little, if any, relation to Heidenhain’s 
later investigations on the secretory pro- 
cesses in the organism. There was, how- 
ever, a single great problem which gave the 
impetus to most of the physiologist’s work. 
“‘Thave endeavored all my life,” he once re- 
marked to the writer, ‘“‘ to learn something 
of the processes which go on in the living 
cells of the body. In my earlier studies I 
selected the muscle cells because of their 
large size. But I soon found that I could 
not reach the desired end by this means 
and accordingly I turned to the secreting 
glands, where I might better observe the 
entire cells under the microscope. Thus I 
have been carried farther and farther.” 
Heidenhain’s researches on the secretory 
processes have become classic, and his mas- 
terly volume on ‘ Absonderungsvorgange ’ 
published in 1883 in Hermann’s Handbuch 
der Physiologie will remain as a permanent 
contribution to physiological literature. 
The experimental researches which form 
the basis for these chapters, and in which 
Heidenhain enjoyed the assistance of a con- 
siderable number of co-workers in his labo- 
ratory, appeared in large part in the 
Studien aus dem physiolog. Institut zu 
Breslau, I.-IV., 1861-1868; in Pfluger’s 
Archiv fiir Physiologie, and in Schultze’s 
Archiv fir Mikroskopische Anatomie. 
The tendency of physiolological research 
SCIENCE. 
[N. S. Vou. VI. No. 148. 
at about the middle of the century had been 
in the direction of a distinctly mechanical 
theory of the secretory processes in which 
the physical forces resulting in filtration 
and diffusion were called upon to explain 
the known phenomena. The prevalent im- 
pression wasin good measure due to the brill- 
iant teachings of men like Briicke and Lud- 
wig, although even the latter appreciated 
many of the difficulties which this aspect 
presented. It was left for Heidenhain to 
emphasize the inadequacy of any universal 
application of the current principles of 
physics and chemistry to satisfy the prob- 
lems presented in the secretory functions. 
He insisted, first of all, on enquiring into 
the specific changes which take place in the 
individual organs incidental to their ac- 
tivity; and here again we discover the 
fundamental notion which was the key- 
note to Heidenhain’s work, namely, the 
desire to investigate the ultimate seat of 
physiological changes, as he expressed it: 
“Das Wesen der lebenden Zelle die uberall 
in urspringlich einfacher oder differenzirter 
Gestalt die Vermittlerin und Tragerin des 
Geschehens ist.’’* In expanding these ideas 
Heidenhain has been occasionally misun- 
stood, or unjustly accused of a belief in 
some ‘vital’ forces which transcend the 
possibilities of natural science. Indeed, I 
cannot refrain from referring to this fact, 
which always aroused regret in him ; for to 
one who is familiar with his work nothing 
can seem more unjustified than this sus- 
picion. No scientist of to-day will deny 
that the processes which go on in the 
living cells, that diffusion through a living 
membrane, is quite a different thing from 
the processes which can be provoked in 
these same elements after their death. 
This, however, does not imply the existence 
of other forces than the chemical and phys- 
ical ones which continually manifest them- 
selves in the inorganic world. It merely 
*Hermann’s Handbuch der Physiologie, V., 11. 
