DEATH AND SENILE DECAY 221 



absorb oxygen nor exhale carbon dioxide. This dormant condition has been 

 termed anabiosis by Preyer, and it is impossible to tell by its appearance 

 whether a dry seed or spore has life latent in it, or whether its vitality has 

 been lost, so that on moistening it decomposes instead of germinating. In 

 spite of their dormant condition, however, certain changes do occur in dry 

 seeds, for when they are kept the power of germination is lost after a 

 longer or shorter time. 



SECTION 64. Death and Senile Decay. 



It can easily be understood that any agency, such as sudden heat or 

 violent pressure, which destroys the structure of the protoplasm, produces 

 immediate death. Furthermore, any functional disturbance which prevents 

 the harmonious co-operation necessary for continued existence ultimately 

 produces unavoidable injury and death. It is in this manner that death is 

 induced by internal causes during the normal progress of development, for 

 although each protoplast strives to maintain its own existence, a vascular 

 plant provides that certain ones, such as tracheae and sclerenchyma fibres, 

 shall die for the common good. The conditions for ultimate death are in 

 fact assured whenever a somatic organ of limited duration commences to 

 undergo its special differentiation. 



Whether death is gradually induced by the external conditions or not, 

 it still remains the final act of life, and is the direct result of the interaction 

 between the properties of the protoplast and the prevailing internal and 

 external conditions. Hence all pathological phenomena are vital reactions, 

 which may, however, go so far as to lead to death. The same methods 

 apply therefore to the study of such phenomena as to vital phenomena in 

 general, and although we may determine the internal or external factors 

 which produce death, their mode of action remains unknown. This 

 is even the case when a single factor, such as the removal of the nucleus, 

 is responsible for the death of the remaining part of the cell. It is, 

 however, rarely the case that the reaction is restricted to a single organ of 

 the protoplast, for in most cases the same agency may affect all of them to 

 varying degrees, and so produce complex internal disturbances. 



We are therefore unable to say whether the fatal disturbances pro- 

 duced at temperatures a little above the maximal point are due to the 

 increased activity of respiration or to a variety of reactions. Furthermore, 

 since the causal origin of respiration is quite unknown, we are equally 

 unable to trace the changes produced by the absence of oxygen which lead 

 ultimately to the death of an aerobe. Nor can we say why the intramole- 

 cular respiration of the latter does not suffice to maintain life, when anaerobic 

 organisms can exist in the entire absence of free oxygen. It is easy to 

 understand that an organism should die when starved, or even when 



