312 PHYSIOLOGY CHAP. 



hypertrophy of the pre-existing fibres, not to hyperplasia or 

 multiplication of their number ; it depends not on an increase in 

 the number or volume of the primitive fibrils, but simply on an 

 increase of the sarcoplasm. He was never successful in finding 

 multiplication of the muscular nuclei. We remarked upon 

 essentially the same fact in the preceding chapter with reference 

 to the muscular fibres of the uterus during pregnancy (Chapter VI.). 

 They are stable elements which last throughout life, becoming 

 hypertrophied or atrophied either as the result of their increased 

 or diminished functional activity or age. 



Kibbert thinks that reproduction through mitosis ceases in 

 many cells when the anaplastic phase the period of growth of 

 the organism as a whole is over. Rabl considers that histological 

 research has proved that the ganglion cells of the nervous system 

 cease multiplying at a very early age, and remain unchanged and 

 without renewal throughout life. I find this morphological fact 

 confirmed by a phenomenon of a psychical nature : the events of 

 early childhood are clearly and vividly remembered up to extreme 

 old age, whereas those which are much more recent readily escape 

 the mind. The grey matter of a child's brain is like a soft 

 phonographic plate on which waves of sound leave deep furrows 

 which time is powerless to efface ; while that of the old is like a 

 similar plate hardened by time and almost incapable of receiving 

 a durable impression of the sounds which fall upon it. Yet it is 

 the same grey matter, composed of the same cells which were 

 formed in earliest childhood and still live in old age, enriched 

 by the choicest fruits of experience and the deep marks of the 

 past life, latent in the dimness of the sub- con scions, and more or 

 less easily summoned into the light of the conscious. 



It is obvious that this longevity of many histological elements, 

 associated with their incapacity to multiply and rejuvenate by 

 division, is the determining cause of their growing old and of the 

 gradual decay which inevitably leads to their death and to that 

 of the organism of which they form part, when their function is 

 a regulating and dominant one, indispensable to the life of the 

 social aggregate represented by the whole organism. 



It is well known that the cells of the embryo and of young 

 persons are as a rule more tenacious of life and possessed of a 

 greater nutritive and germinative capacity than are those of the 

 old. Even in old people, however, many cells are capable of repro- 

 duction ; were this not the case, all processes of repair would be 

 impossible in old people and even the slightest surgical operation 

 would be undesirable. We are therefore forced to conclude that 

 death, whether from disease or from natural causes, takes place 

 when the central regulating and dominant organs, on which the 

 life of the whole organism depends, cease to act owing either to 

 morbid changes or to old age. 



