62 



SCIENCE 



[N. S. Vol. XXVII. No. 680 



physical side, after preliminary work by 

 Poneelet and Sadi-Carnot, Joule, Thomson 

 and Clausius reached the same grand con- 

 ception. The first to enunciate clearly and 

 fully the doctrine of the conservation of 

 energy and to measure the unit of mechan- 

 ical work derived from heat was the physi- 

 cian, J. R. Mayer. Joule 's work completed 

 the demonstration, but Mayer's name is 

 deservedly attached to this principle by 

 Poincare and others, as Lavoisier's is to 

 that of the conservation of mass, and Sadi- 

 Carnot 's to the principle of degradation of 

 energy. As regards this last principle it 

 is almost as interesting to biologists as to 

 physicists that in the so-called Brunonian 

 movement, discovered by the physician and 

 more eminent botanist, Robert Brown, and 

 the subject of interesting physical investi- 

 gations in recent years, we behold an ap- 

 parent exception to the principle of deg- 

 radation of energy, such as Clerk Max- 

 well pictured as possible to the operations 

 of his sorting demon. 



I must forego further citation of ex- 

 amples of this kind of correlation between 

 the work of physicists and of physiologists, 

 and leave untouched the chemical side, 

 which is much richer in similar illustra- 

 tions. The significance to organic chem- 

 istry of the synthesis of urea by Wohler, 

 and to agricultural chemistry of the bac- 

 teriological studies of nitrification in the 

 soil and fixation of nitrogen in plants, will 

 perhaps indicate how large and fascinating 

 a field'! must pass by. 



The great advances in physics and chem- 

 istry initiated in France toward the end 

 of the eighteenth and beginning of the 

 nineteenth century were quickly reflected 

 upon the medical and biological sciences 

 through influences which in large part are 

 attributable to this new movement in phys- 

 ical science. New methods of physical ex- 

 amination of the patient were introduced, 

 and pathology and experimental and chem- 



ical physiology were developed as biological 

 sciences of the first rank. This reforma- 

 tion of the medical sciences in the first 

 third of the nineteenth century was mainly 

 the work of Frenchmen, the great names in 

 this development being those of Lavoisier, 

 Bichat, Laennec and Magendie, the last a 

 friend and physician of Laplace, and con- 

 temporary of Cuvier, who represented a 

 like movement in zoology. Liebig, the 

 pupil of Gay-Lussac and founder of bio- 

 logical chemistry as a distinct science, car- 

 ried in the third decade of the century the 

 new spirit to Germany, where Johannes 

 Miiller and his pupils became the center of 

 a movement which rescued medicine and bi- 

 ology from the shackles of the philosophy of 

 nature and has given Germany the suprem- 

 acy in these fields of science. The experi- 

 mental physiological work of the brothers 

 Weber, two being physicians and the third 

 the great physicist who was so intimately 

 associated with Gauss in Gottingen, was of 

 great influence in introducing the physical 

 direction of physiological research, but 

 Magendie stands first in making the experi- 

 mental method the corner-stone of normal 

 and pathological physiology and pharma- 

 cology. 



Most pertinent to my theme is it to note 

 that the light which has transformed the 

 face of modern practical medicine came in 

 the first instance not from a physician but 

 from a physicist and chemist, Pasteur. 

 The field of bacteriological study was 

 placed on a firm foundation and thrown 

 open to ready exploration by Robert Koch, 

 and thereby that class of diseases most im- 

 portant to the human race, the infectious, 

 became subject in ever-increasing measure 

 to control by man. Thus hygiene and 

 preventive medicine, through their power 

 to check the incalculable waste of human 

 life and health and activities, have come 

 into relations, which have only begun to be 

 appreciated, with educational, political, 



