189S] 



NOTES AND COMMENTS 147 



animals to light are identical with the heliotropic phenomena in 

 plants. Hence it is a mistake to ascrihe such r(uictions as the flying 

 of the moth into the flame to specific functions of the brain and the 

 eyes. Sleep is a phenomenon which occurs in insects and plants, 

 and it would be waste of time to attempt an explanation of sleep 

 on the basis of phenomena of circulation. The best interests of 

 physiology and pathology demand that the systematic development 

 of comparative physiology be one of the physiological problems of 

 to-day." 



STEREOCHEMISTHY and PHYSIOLOCrY 



The chemical changes that take place in connection with life and 

 the gradual organisation of living matter are phenomena that the 

 physiologist of to-day is trying hard to connect. In his attempt he 

 may be aided, says Dr Loeb, by two series of facts : " (1) The fact 

 that phenomena of fermentation lead to an increase in the 

 number of molecules and thus bring about an increase of osmotic 

 pressure in the cells, this increase of osmotic pressure being the 

 source of energy for the work of growth ; (2) the facts of 

 heteromorphosis, i.e., the possibility of transforming in certain 

 animals one organ into another or substituting one organ for 

 another through external influences, such as gravitation, contact, 

 light, etc." 



" The exact and definite determination of life phenomena which 

 are common to plants and animals is only one side of the physio- 

 logical problem of to-day. The other side is the construction of 

 a mental picture of the constitution of living matter from these 

 general qualities. In this portion of our work we need the aid of 

 physiological chemistry and especially of three of its theories — 

 stereo-chemistry, Van't Hoflf's theory of osmotic pressures, and the 

 theory of the dissociation of electrolytes. We know that the 

 peculiar phenomena of oxidation in living matter are determined 

 by fermentative processes, and we venture to say that fermentations 

 form the basis of all life phenomena. It has been demonstrated 

 that fermentability is a function of the geometrical configuration of 

 the molecule. Saccharoiiiyces Cerevisiae is a ferment for such sugars 

 only as have three, or a multiple of three, atoms of carbon in the 

 molecule. Among the hexaldoses only 5-glucose, 5-mannose, and 

 ^-galactose are fermentable, while their stereo-isomers are not 

 fermentable. But the influence of the geometrical configuration 

 »oes farther. Voit has suggested and Cramer has demonstrated 

 that there is a far-reaching parallelism between the fermentability 

 and assimilation of carbohydrates. Higher animals as well as yeast 

 cells are able to form glycogen from such carbohydrates as are 

 fermentable by yeast. The further development of these stereo- 



