4 NATURE AND RELATIONS OF AN ORGANISM 



rigor. These extreme variations in the environment may, or 

 may not; be followed by death. Thus spores of bacteria, and 

 seeds have been subjected to a temperature of liquid hydrogen 

 (—252° C.) and when restored to normal temperatures resumed 

 their functions in full. This experience invalidates the older con- 

 ception of protoplasm as a substance essentially and indispensa- 

 bly in a constant state of adjustment to its environment, since it 

 is impossible to estimate any molecular motion at the low temper- 

 atures named. As a matter of fact the adjustments or transfor- 

 mations of protoplasm may be all reduced or totally inhibited, 

 and it may still retain its definite character. 



Secondly it is to be said that rapid changes in the incident con- 

 ditions induces variations in the performance of the functions, or 

 morphological activities of living matter. The amount of such 

 change does not bear a direct proportion to the amount of the 

 incident force received by the living matter, and in certain in- 

 stances may be directly inverse to it. This relationship has to do 

 wholly with the extra-chemical and physical organization of proto- 

 plasm, and constitutes irritability. Irritability is that property of 

 living matter by which it responds to an impinging force by the 

 release of an amount of energy disproportionate in intensity and 

 range of molecular motion, and is fairly illustrated by the me- 

 chanism of a rifle, or engine in which an enormous power may be 

 released by a simple pull on a trigger or lever. The energy set 

 free by the impinging force constituting the stimulus, may be 

 manifested by alterations in the functions or by alteration, sup- 

 pression, or multiplication of the organs of the plant, according to 

 the transformations set up in the organism (10). 



Trophic forces may act with such intensity of mechanical or 

 chemical effect as to produce actual lesions or disintegration of the 

 protoplasts, as in wounds, corrosive chemical action, or desicca- 

 tion, electrocution, etc. 



4. External Forces to which Protoplasm Reacts. The principal 

 forces to which living matter responds in the methods described 

 above are : — shock, contact, pressure, traction, chemical action, 



