or animal, and that it is only formed through the physiological 

 activities of living organisms. In the absence of life, protoplasm 

 cannot be formed, and, so far as we can perceive, there are no 

 manifestations of life without it. 



Living substance or protoplasm must be looked upon as con- 

 stantly undcrgoii.g changes that vary with the functions required 

 of it. These changes, without attempting to distinguish between 

 them, as chemical, physical, or more strictly speaking, biological, 

 are most conveniently expressed by the general term metabolism 

 which is both constructive and destructive. 



Dr. M. Fostei says : " We may picture to ourselves this total 

 change, which u e designate by the term metabolism, as consisting, 

 on the one hand, of a downward series of changes (katabolic 

 changes), a stair of many steps, in which more complex bodies are 

 broken down into simpler and simpler waste bodies, and on the 

 other hand, of an upward series of changes (anabolic changes), as 

 also a stair of many steps, by which the dead food, of varying 

 simplicity and complexity, is, with the further assumption of 

 energy, built up into more and more complex bodies. The summit 

 of this stair we call protoplasm." 



AH work implies waste, and the work of life results, directly or 

 indirectly, in the waste of protoplasm. Every word uttered by a 

 speaker costs him some physical loss, and, in the strictest sense, 

 he burns that his hearers may have light — so much of his body 

 resolved into carbonic acid and urea.* It is one of the funda- 

 mental doctrines of physiology that every part of our organism 

 has its own definite term of vitality, and that ihere is a continuous 

 succession of the destruction of old cells and the formation of new 

 ones in all tissues, and especially in those in which the most active 

 vital changes are going on, as, for example, in the nervous and 

 muscular tissues. Even the most solid portions of the animal 

 frame, such as the bones, and, to a less extent, the teeth, are under- 

 going a perpetual, although slower change of this nature, and 

 throughout the body there is a continuous removal of effete or 

 worn-out tissues, and a corresponding deposition of new matter. 

 Every blow we strike, every thought we think, is accompanied by 

 the death and disintegration of a certain amount of muscular or 

 nervous tissue as its necessary condition, and thus every action of 

 our corporeal life, from its beginning to its close, takes place at the 

 expense of the vitality of a certain amount of organized structure. 

 This we term molecularf death. It must be clear to every intelli- 





* It is said that urea circulates in the blood, and is excreted by the kidneys, and the 

 more mental work the more urea is produced. A fretfulness that produces activity, but 

 no actual results, causes a loss of just so many grains of urea. Therefore, for every 

 footpound of thought you will have a given amount of urea excreted. 



t Speaking of molecules, scientists state that a cubic inch of oxygen, at ordinary tem- 

 perature and pressure, contains so many molecules, that a number equal to the popula- 

 tion of our globe might escape every second, and it would take over six thousand years 

 to empty this small space. Or if a single drop of water could b3 rtiagnified to the 

 si^e of the earth, the molecules woul '. be the size of biUia,rd balls. 



