MECHANISM AND VITALISM 409 



compounds in the laboratory has progressed by enormous strides. 

 Even some of the products of the ductless glands (hormones), e. g., 

 thyroxin, have been synthesized, so that this synthetic property 

 can no longer be considered as forming a line of demarcation be- 

 tween the organic and the inorganic. 



Disputed Points. — Other arguments have been put forward 

 by the vitalists, and other qualities have been pointed out as dis- 

 tinctive of living matter. Among these may be mentioned the 

 power of growth, reproduction, metabolism, irritability, autoregu- 

 lation, and heredity, but to all of these the mechanists claim to 

 have discovered analogies or homologies in the inorganic world. 

 Growth, say the mechanists, is largely increase in size due to the 

 addition of water. A dry, dead board grows by imbibition, and 

 the swelling of a membrane filled with sugar solution, when thrown 

 into a jar of water, is essentially the same thing as the growth of 

 the cell. The addition of material or the increase of dry weight in 

 organic growth is analogous to the growth of crystals, and differ- 

 entiation may be seen in the formation of growth membranes pro- 

 duced by inorganic compounds when placed in contact with each 

 other (Chap. XIX). 



Reproduction in its essentials is the separation of a bit of proto- 

 plasm which is capable of living independently and which has the 

 same properties as the parent from which it came. With the 

 proper combination of chemicals and the help of surface ten- 

 sion changes, it is possible to get a drop to divide in two. 

 The resultant drops possess the properties of the parent sub- 

 stance and, say the mechanists, thus show the essence of repro- 

 duction. 



The characteristics of irritability are the delayed response and 

 the expenditure of stored-up energy in making the response, but 

 these are shown equally well by dynamite, by a motor, and in a 

 thousand other ways. In setting off a stick of dynamite, the " im- 

 pulse" is given when the match is struck and applied to the fuse. 

 While the fuse is burning, the impulse or "stimulus" is traveling 

 to the stick, and when the explosion occurs, this delayed response 

 expends much more energy than it took to apply the match. 



By autoregulation we mean the way in which the organism ad- 

 justs itself to changes in the external environment in order to 

 keep the internal environment constant. The human body has 

 a temperature of 98.6° F. Any increase in the external tempera- 



