> ^PHYSICAL CHEMISTRY IN MEDICINE. 



oi v the^ : m6chaiiLcal equivalent of heat, while through 

 HELMHOLTZ was developed and executed the most 

 extensive programme for the application of the law of 

 energy to all subjects. 



The penetrative analysis of thermodynamical phenom- 

 ena by CLAUSIUS and THOMSON completed the subject 

 with the establishment of the so-called chief laws of 

 thermodynamics. 



The transformations in energy in chemical reactions 

 have in general two sources. As is well known every 

 change in the state of aggregation is accompanied by 

 either an absorption or an evolution of heat. Since 

 changes in physical state often accompany a chemical 

 reaction, these constitute therefore one of the sources 

 of the transformations in energy accompanying this 

 reaction. 



A second is found in the chemical reaction itself. 

 The synthesis or analysis of a substance 13 accompanied 

 by a thermal change which may have eimer a positive 

 or a negative value. To illustrate this we may cite the 

 formation of a salt from an acid and a base with the 

 development of the so-called heat of neutralization; or 

 the decomposition of a salt into its components with a 

 using up of electrical energy. 



All these metamorphoses in energy constituted from 

 the first a fruitful field for work, in which medicine 

 also soon took part. While, however, the decrease 

 in the potential energy of the foodstuffs in the metabolism 

 of men and the higher animals constitutes one of the 

 best developed chapters of medicine, calorimetric in- 

 vestigations of the culture media of bacteria are still 

 lacking, and this in spite of the fact that this subject 



