262 ZOOLOGICAL PHILOSOPHY 



height of its vigour, but it grows no more. Now the surplus of the 

 parts prepared, being of no further use for nutrition or growth, is 

 destined by nature to another purpose, and becomes the source 

 through which she arranges for the reproduction of new individuals 

 Hke the others. 



Hence reproduction, the third of the vital faculties, derives its 

 origin like growth from nutrition, or rather from the materials pre- 

 pared by nutrition. But this faculty of reproduction only acquires 

 intensity when the faculty of growth begins to decline : this fact is 

 confirmed by common observation, since the reproductive organs 

 (sexual parts) both in plants and animals only begin to develop when 

 the growth of the individual is nearing an end. 



I should add that, since the materials prepared for nutrition are 

 assimilated particles of as many different kinds as there are parts in the 

 body, the union of these diverse particles left over from nutrition and 

 growth constitute the elements of a very small organised body, exactly 

 similar to that from which it sprang. 



In a very simple living body with no special organs, when nutrition 

 has attained the Hmit of growth for the individual, the excess is then 

 diverted to the formation and development of a part which thereupon 

 separates from the organism and continues to live and grow, constitut- 

 ing a new individual like the old one. Such indeed is the method of 

 reproduction by fission and by gemmae or buds, which occurs without 

 any need for a special organ. 



Ultimately after a still longer period — a period that varies even in 

 the individuals of one race according to their habits and climate^ 

 the most supple parts of the hving body acquire so great a rigidity and 

 suffer so great a diminution of orgasm, that nutrition thereafter repairs 

 the losses only incompletely. The body then gradually wastes away ; 

 and if some slight accident or some internal disorder, that the diminished 

 vital forces cannot cope with, do not put an end to the individual, 

 its increasing old age is necessarily terminated by a natural death 

 which supervenes when the existing state of things no longer permits 

 of the performance of organic movements. 



This rigidity of the soft parts, which increases during life, has been 

 denied on the ground that after death the heart and other soft parts 

 of an old man shrink more and become more flaccid than in a child or 

 young man who has just died. But the fact has been overlooked that 

 orgasm and irritability which still continue sometime after death, 

 lasts longer and is more intense in young individuals than in the old, 

 among whom these faculties are greatly weakened and are extinguished 

 almost simultaneously with Ufe. This cause alone gives rise to the 

 observed effects. 



