vii THE STAGES OF LIFE AND DEATH 299 



and the refuse of the tissues ; it not seldom happens, however, 

 that under the stimulus of poisons present in the blood (such as 

 the toxins of infectious diseases, alcohol, the poisons of intestinal 

 putrefaction, especially of protein substances, endogenous and 

 exogenous poisons generally), they go beyond their proper sphere 

 of activity, destroying and absorbing the higher cells of the 

 organism, for which nothing but connective tissue can be substi- 

 tuted, hence the sclerosis of the organs of old people. Metschnikoff 

 believes that his microscopic researches have enabled him to 

 discover the macrophages which surround the ganglion cells and 

 those of the kidneys, liver, bones, and contractile substance of the 

 muscles, etc. The mechanism of senile atrophy therefore is just 

 like that of atrophy due to the action of bacteria or toxins, hence 

 the doctrine of the pathological genesis of old age. 



But if we look at it more closely, this doctrine is an abuse of 

 the theory of phagocytosis. Even if it be granted that the 

 macrophages work the havoc in the different elements which 

 they are said to do, and hasten their dissolution, this fact would 

 be merely a secondary phenomenon, and would shed no light on 

 the essential fact of senility. Further, many histologists and 

 neuropathologists refuse to admit the discoveries and microscopic 

 figures with which Metschnikoff supports his theory; Cerletti 

 (1903) bluntly terms them errors of observation. He examined a 

 large number of senile brains belonging to persons who had died 

 at over 90 years of age with pronounced atrophy, and found 

 no sign of special phagocytic activity in the ganglion cells. On 

 the other hand, he found the conditions discovered by Metschnikoff 

 in the brains of young people which showed no sign of atrophy. 

 The supposed macrophages are according to him merely glia cells, 

 which are found also under normal conditions near the ganglion 

 cells (satellite cells, the Trabantzellen of German scientists). Von 

 Hansemann (1907), Saigo, and others came to the same conclusion 

 and noticed the same appearance in individuals of all ages. 



Salimbeni and Gery, who belong to Metschnikoffs school, have 

 recently made an accurate anatomical and histological study of 

 a senile organism ; they found in tlie various sclerosed tissues 

 mononuclear and macrophagic infiltration, cellular degenerations 

 in the liver and pancreas, hypoplasia of the adenoid organs, and 

 calcification of the blood-vessels, the choroid plexuses, and the 

 medulla. The hypophysis and the thyroid gland showed signs of 

 decreased functional activity, and the supra-renal capsule those of 

 over-activity. The most important and the most widespread 

 of all these lesions is sclerosis, which leaves no organ unapared 

 and is due to mononuclear and macrophagic infiltration. 



These various forms of deterioration cannot all be explained 

 by auto-intoxication arising in the intestines, for it fails to 

 account for the fact that certain organs, especially the genital 



