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At the former university he graduated in September 1851. 
As early as the year 1852 he worked as prosector under 
C. Ludwig, whose close friendship he retained throughout 
life. 
In 1856 he went into residence at Ziirich, and, in suc- 
cession to Ludwig and Moleschott, obtained in 1862 the 
full professorship of physiology there, which he retained 
for six years. Inthe year 1868, upon Von Bezold’s early 
death, Fick was called to Wiirzburg, where he filled the 
chair of physiology for thirty-one years. He resigned 
his post at the end of the summer term of 1899, not from 
distaste for work or through the burden of years, but 
while in full vigour of mind and body, in the strict fulfil- 
ment of a long-expressed intention of making way, on 
the completion of his seventieth year of life, for the 
energies of a younger man. 
At the time when Fick entered upon the study of 
physiology, modern medicine, as it is now understood 
and taught in the schools, was still in its infancy. The 
great strides made by chemistry at the beginning of last 
century had rendered possible the introduction of exact 
methods in the investigation of the problems of biology. 
The first positions securely gained by physical science 
had been at once utilised to set aside the doctrine of 
“vital power,” and to establish the important principle 
that we must endeavour to explain the specific phenomena 
of life as being determined by preceding chemical and 
physical conditions. Just as the chemists Lavoisier, 
Liebig and others, with the knowledge that they had won 
by their special training, addressed themselves at once 
to the solution of biological questions, so a school of 
physicists, starting from the basis of its own discoveries, 
proceeded to the investigation of the physiological 
problems which appertained to it. The brothers Ernst, 
Heinrich and Eduard Weber, Helmholtz, Du Bois-Rey- 
mond, Ludwig, Briicke, are the most prominent names 
of this school and already belong to history, and amongst 
these earlier adaptors of the methods of physical research 
to the study of biology, Fick must be accorded a place 
on account both of his conspicuous bent and training as a 
physicist and of the work accomplished by him. So 
early asthe year 1849, when a nineteen-year-old student, 
Fick published his first scientific treatise—that on the 
muscular system of the thigh—an essay which even at 
the present day forms a. very instructive analysis of the 
mechanical relations of the muscles of the hip joint. 
For these researches into the mechanism of the human 
body Fick always retained a liking. He wrote a mono- 
graph on the saddle-shaped articulations, gave in his 
“Medical Physics,” the first edition of which appeared 
in the year 1856, an admirable exposition of the 
mechanism of the joints generally, and contributed an 
article on the subject. to L. Hermann’s great ‘‘ Hand- 
buch,” besides encouraging several of his own pupils to 
undertake similar investigations. 
His scientific work upon the mechanics of the body led 
Fick to a special line of inquiry—one to which he devoted 
the working time and energy of his mature years—that 
respecting the changes of muscle during its contraction. 
There are about thirty essays by Fick-himself, as well as 
a number of writings by his students, which deal with 
particular points in the physiology of muscle. Of these 
one of the most important was the development of heat 
which attends contraction. With the aid of thermo- 
electrical apparatus devised by himself, he was enabled 
to determine approximately the absolute amount of heat 
that was developed during continuous contraction. He 
subsequently introduced and defined the important con- 
ceptions which are expressed by the terms “ isotonic” 
and “isometric” as applied to contraction, and investi- 
gated the nature of the conditions so designated. . For 
the measurement of work, he constructed his “ Arbeits- 
sammler.” 
As the final result of all his muscular studies, he stated 
NO. 1703, VOL. 66] 
his views as to the nature of the process of muscular con- 
traction. These have not escaped criticism. One of his 
conclusions, however, which in a manner he reached by 
a process of exclusion in so faras he rendered untenable 
other possible ways of explaining the contraction of muscle 
by reference to the second of the laws of the mechanical 
theory of heat, is, indeed, of quite prime importance. 
According to Fick, the kinetic energy generated by 
chemical reactions in the muscle cannot be accounted 
for by the hypothesis that the chemical energy consumed 
is first developed in the form of heat, and this transformed 
into the coordinated kinetic energy of the contraction. 
It must rather be supposed that the chemical forces 
stored up in the muscle are so coordinated that in their 
transformation into kinetic energy they directly cause the 
change of form ofthe muscle ; so that we have not to do 
with a thermodynamic process as in the case of the 
steam engine, but the chemical energy is converted 
directly into the coordinated kinetic energy of the con- 
traction. With this notable definition respecting the 
changes which precede muscular contraction, an im- 
portant stage is reached in the explanation of the 
phenomena of contractile substances, and every future 
discussion of these questions must be referred back to 
this as a starting point. 
Another subject of Fick’s repeated investigations was 
that of the dynamics of the circulation. His first efforts 
were directed towards improving the methods of obtain- 
ing graphic records of the blood-pressure curve, with the 
result that the manometer and the spring kymograph 
bearing his name have been adopted into general use. 
He was the first to analyse by means of an apparatus 
constructed by him—now called the plethysmograph— 
and with the greatest clearness and precision, the varia- 
tions in speed of the flow of blood in artery and vein 
(Ztirich Laboratory Reports, 1868). By means of new 
methods of investigation and observation he threw 
valuable light upon the phenomenon of dicrotism and 
upon the pressure of the blood in the ventricles of the 
heart and in the great vessels. 
Under the head of the physiology of the organs of 
sense, he paid special attention to the subject of vision. 
His dissertation “Tractatus de errore optico,” &c., 
Marburg, 1851, deals principally with the phenomena of 
astigmatism (Helmholtz, ‘“ Physiolog. Optik,” p. 147). 
Fick occupied himself repeatedly with speculations as to 
the explanation of the colour sense. He published a 
number of critical and experimental studies upon the 
subject. His last communication to the Society of 
Medical Physics of Wiirzburg dealt with Hering’s theory 
of the colour sense. His contributions to the study of 
the subject of hearing consisted in an experimental 
investigation upon the mechanism of the tympanum. 
A paper by Fick, on the sense of touch, is comprised in 
the volume for 1860 of Moleschott’s Uztersuchungen. 
, Upon the physiology of the nerve substance Fick 
published only a few essays. To the issues for the year 
1862 and 1864 of the reports of the Vienna Academy and 
to the E. H. Weber “ Festschrift” in the year 1871 he 
contributed studies upon the sensibility of the spinal 
chord. The essay upon the different degrees of excita- 
bility observable in functionally different parts of the 
chord deserves special mention. 
Of Fick’s work on metabolism, and the physiology of 
the digestive glands, may be mentioned, as particularly 
well known, the experiment* that he made with the 
1 Vide the Philosophical Magazine for June 1866. The late Sir Edward 
Frankland regarded this as “‘one of the most important chemico-physio- 
logical experiments ever made” (Frankland’s ‘t Experimental Researches,” 
p. 918). Although prevented from accompanying his brother-in-law, Fick, 
on the expedition, Frankland undertook the experimental determination of 
certain calorimetrical equivalents required as a basis for the conclusions 
drawn from the Faulhorn experiment. These, it may be added, had a 
much wider application, and until replaced by more exact determinations 
they served for years as the only data on which calculations could be 
founded. 
