THE EVOLUTION OF DEATH 79 



no individualities as in the higher animals. A part of a 

 sponge or of a coral may die and the other part continue living, 

 because the correlation of the parts has not advanced so far, 

 but in these animals preservation of the whole is independent 

 of the preservation of the correlation. In the higher animals 

 the correlation is much more intimate, and therefore individ- 

 uality more marked, until we reach an animal whose parts 

 work together and must reach definite proportions in order 

 that the working together may be properly carried out. An 

 organism which has attained higher development in this way 

 cannot continue its life if an essential part or an essential 

 organ becomes incapable of functioning. We know that the 

 single organs must have their specific differentiation, and we 

 know further that these diflEerentiations in the majority of 

 cases increase with age, and that it may go so far that the cells 

 of a special organ cannot function any longer. Now if an 

 organ which is essential for the maintenance of the whole 

 body gives out, the entire animal must die. It is a priori 

 improbable that in all cases natural death is a consequence of 

 the alterations of the same organ. Thus we know that in 

 certain insects and worms death occurs almost suddenly after 

 the discharge of the sexual products, yet their nervous system 

 may be intact. We may admit that physiological death in 

 man is caused by the breakdown of the nervous system, and 

 yet the practicing physician sticks to his opinion that death 

 in extreme old age occurs more frequently through failure of 

 the blood vessels. We must heed the fact that even in the 

 highest animals, just as in sponges and coelenterates, parts of 

 the body may break down without causing physiological 

 death. Permit me again to direct your attention to the fact 

 that in man not merely single cells but even entire organs may 

 die oflf. In its essence the phenomenon in these cases is the 



