318 PROGRESS OF SCIENCE IN THE CENTURY. 



chemical bodies are present. The elements of which 

 they consist are only such as exist in the inanimate 

 world also, but their number is small, and it is chiefly 

 the elements having the lowest atomic weights that 

 compose living substance. A special vital element 

 does not exist, but the compounds in which these 

 elements occur are characteristic of living substance, 

 and in great part are absent from the inorganic world. 

 They are, first of all, proteids, the most complex of all 

 organic compounds, which consist of the elements car- 

 bon, hydrogen, oxygen, nitrogen, and sulphur, and are 

 never wanting in living substance. Further, there 

 occur other complex organic compounds, such as carbo- 

 hydrates, fats, and simpler substances, all of which 

 either are derived from the decomposition of proteids or 

 are necessary to their construction; and inorganic sub- 

 stances, such as salts and water ; the latter gives to living 

 substance its requisite liquid consistency." * 



It has to be remembered that living substance must 

 be killed before it is chemically studied, and that 

 we have no means of knowing how rapidly changes 

 of molecular arrangement may occur after death. 

 But, as Verworn says, " the biting sarcasm that 

 Mephistopheles pours out before the scholar upon 

 this practice of physiological chemistry must be quiet- 

 ly endured." 



Although we do not know the nature of living 

 matter — either in its simplest expression in the 

 Protist gliding in the pond, or in its highest ex- 

 pression when its activity in our brains is associated 

 with thought — we are not without data in regard to 

 the sequence of vital processes. We can trace, by- 

 chemical analysis, at least some of the steps by which 

 food is transformed until it becomes a asable part 



* Prof. F. S. Lee's translation of Prof. Max Verworn's 

 General Physiology, 1899, p. 117. 



