RESEARCH IN MEDICINE 551 



stance (urea) dates our modern organic chemistry. Liebig represent- 

 ing the school of Gay-Ltissac and Wohler that of Berzelius, one at 

 Giessen and the otlier at Gottingen^ serve as an interesting example 

 of scientific cooperation to develop a new science. 



Liebig's work led directly to those activities which we now group 

 under the term physiological or biological chemistry, but physiology 

 was at this time making rapid strides along another line of attack — the 

 application of the principles of mechanics and physics. The part of 

 physics in medicine from Galileo to Eoentgen is one of the most fasci- 

 nating phases of the history of medicine; in principle and practise, in 

 theory and science, its influence has been one of fundamental importance 

 and in its application to methods of clinical diagnosis it shares equally 

 with pathological anatomy in the awakening of modern clinical medi- 

 cine. The first widely reaching application was in Harvey's interpre- 

 tation of the circulation of the blood and the action of the heart, but it 

 was not until organized physiological laboratories had been instituted 

 that the application of the principle of physics bore abundant fruit. 

 To recall the state of physics at that time it is only necessary to state 

 that the work of Galvani and Volta was completed and that Ampere 

 and Ohm, Faraday and Wheatstone, were still active. Charles Bell had 

 already (1811) given to England the second of two great discoveries in 

 physiology, the differentiation of sensory and motor nerves. Haller, as 

 we have seen, had in the preceding century presented and discussed the 

 irritability of muscle. The time was at hand for the study of the gen- 

 eral physics of muscle and nerve and the special senses. Ernst Weber 

 announced the principles of his psycho-physics in 1825 and Johannes 

 Miiller those of his physical chemistry in 1826 ; Purkinje had already 

 established the first university laboratory of physiology in 1824 at Bres- 

 lau; in 1838 the celebrated physiological institute at Berlin was formed 

 under the direction of Miiller and in 1840 Ernst Weber was made pro- 

 fessor of physiology at Leipzig. From these two centers, Berlin and 

 Leipzig, from Johannes Miiller and Ernst PL Weber, came a great vol- 

 ume of minute investigations based on exact methods of inquiry. Both 

 schools were largely busied with studies of the mechanism of the per- 

 ceptions of the senses, that of Weber tending to include mental phe- 

 nomena, thus anticipating the modern school of psychologists, that of 

 Miiller including not only the methods of physics, but also those of 

 general biology. Miiller (1801-1858) was indeed the last of a school 

 which attempted to embrace all of the territory of biology in its broad 

 sense; a territory which now has its separate and distinct fields of 

 morphology, physiology and chemistry. He may, however, be regarded 

 as responsible for some of the divisions into which the older biology has 

 been split, and for the impulse to new lines of study, for he was the 

 teacher of the masters who came in time to occupy high places in biol- 



