300 PHYSIOLOGY CHAP. 



organs of women, undergo a process of involution at a certain 

 period, quite regardless of the kind of life led by the individual. 

 The various cellular degenerations in the glands of internal 

 secretion cannot all be due to one and the same cause ; moreover, 

 a fundamental fact in the process of growing old the gradual 

 slackening and final cessation of cellular reproduction is still 

 shrouded in mystery. 



We have paused to consider Metschnikoff' s teaching, because 

 this writer has drawn from it practical conclusions which have 

 been received with great interest by the laity. The ancient 

 maxim of Cicero that we must struggle against old age as we 

 would against infirmity has been adopted once more, and the 

 proposal has been made to check the development of bacteria in 

 the intestines, not merely by means of moderation in food, but 

 also by the habitual use of various forms of fermented milk 

 (the kephir of the Caucasus, the koumis of Eussia, the yoghurt of 

 Bulgaria, the gioddu of Sardinia), and by the administration of 

 cultures of bacteria producing lactic acid, so as to check or 

 prevent intestinal putrefaction. 



Whatever may be the practical value of his hygienic precepts 

 (one of which, moderation in food, is excellent and supported by 

 the latest scientific researches), it is obviously both useless and 

 erroneous to expect that they will enable us to avoid the effects 

 of old age, which is, as we have already said, not a morbid process 

 due to intoxication, but an inevitable physiological process of 

 involution. 



VII. In order to understand the causes of natural death, we 

 must have a scientific idea of the physical basis of old age which 

 gradually prepares the way for it. The changes which age brings 

 about in our organism consist of atrophic processes affecting all 

 our organs to a greater or less extent, no matter whether they 

 have been subject during life to the influence of disease of either 

 a transitory or chronic kind. The constancy with which atrophy 

 of all the organs is noted in old age is regarded by J. Cohnheim 

 as a proof that it is a physiological involution (Preyer's cata- 

 plastic phase). C. S. Minot also, in his studies on growth, comes 

 to the same conclusion. 



The entire organism of the aged presents certain character- 

 istics and physical features which have inspired the art of the 

 greatest painters and the poetical realism of Baudelaire. The 

 approach of old age is almost always heralded by a falling off in 

 weight, accompanied by more or less pronounced anaemia (senile 

 anaemia). The blood becomes poorer in erythrocytes and haemo- 

 globin (Solokoff) ; the proportion between white and red globules 

 may exceed 1 : 650 ; the resistance of the blood corpuscles diminishes 

 especially after the seventieth year (Obici). Excessive stoutness 

 is seldom seen in old people (Bichat). 



