PRESIDENT’S ADDRESS. 413 
and Claude Bernard in France. In 1847 the four first met together 
in Berlin. Ludwig used often to speak of this, and say, ‘‘ We 
four imagined that we should constitute physiology on a chemico- 
physical basis, and give it equal scientific rank with physics.” 
Reviewing physiology at the present day, after the lapse of fifty 
years, although it is certain that the efforts of these men and their 
pupils—for so many physiologists in Europe and America were 
directly or indirectly pupils of one of these men—may not have 
succeeded in placing physiology on the same level with physics as 
an exact science, yet they have enormously advanced all physio- 
logical observations in the direction of accuracy. Their partial 
success is due to the much greater complexity of the problems to 
be solved, and the greater difficulty in obtaining exact measure- 
ments, and not necessarily to less accuracy in’ experimental 
methods. 
Incidentally, too, it is reassuring to remember that these men, 
working at physiological problems, have done yeowan service to 
physics. Ludwig first introduced the graphic method of recording 
any movement upon a travelling surface, which is at present in 
use in every physical laboratory, and indeed universally applied ; 
and Helmholtz published his famous essay on the conservation 
of energy (Erhaltung der Kraft) whilst still a physiologist. 
The determination of these men to systematically attack physio- 
logical problems by the methods of chemistry and physics is often 
spoken of as a revolution. Like other revolutions, however, 
history shows that it was not such a sudden transition as has 
been stated. True, the physiology antecedent to this date was 
rather too much inclined to fall back upon the phrase “ vital 
force,” and to accept a teleological reason as the explanation of 
phenomena concerning living organisms; but there had been 
physiologists such as Stephen Hales, Poiselle, Majendie, Weber, 
and Johannes Miller, who certainly tried to measure physiological 
phenomena in much the same way as was apphed in physics, and 
Liebig, indeed, regarded a considerable portion of physiology as 
simply a branch of chemistry. The splendid impetus given to 
physiology about this period appears to me to be due, not to an 
entirely new way of approaching its problems, but to the vast 
superiority of the experimental methods employed. In other 
words, the advance was due, not so much to change of direction, 
but to superior tactics. 
I will now endeavour by two or three examples to represent to 
you the kind of work physiologists have been doing during the 
past fifty years. 
At the outset, I may say that until comparatively recently the 
physiological investigation of the last half century has been almost 
confined to the study of function in the higher animals. Unlike 
Miller, who experimented upon every kind of animal backboned 
