OLD AGE AND DEATH 375 



no sclerosis or hardening ; the muscles and the heart 

 were quite normal, and so on. It goes without saying 

 that we must not generalise on one parrot, and very few 

 aged parrots have been scientifically utilised; but the 

 fact is quite clear that this octogenarian was very sound 

 in most of its organs. It would have passed even a strict 

 Insurance Examiner on all points save one, and that 

 happened to be detected because the scientific eye was 

 predisposed to see. 



Only in the fore-brain was there anything very note- 

 worthy its nerve-cells were in many places surrounded 

 with nerve-devouring phagocytes. These " neuronophagous 

 cells " are well known in the brains of patients suffering 

 from certain neurotic diseases and from persistent intoxica- 

 tion ; they are also frequent in the brains of old men and 

 old mammals, but the authors never saw a case so marked 

 as that of this aged parrot. There seemed to be " an 

 intense phagocytosis" the brain was being literally "de- 

 voured " by the " neuronophages." The noblest elements 

 of the organisation were falling victim to cells of the most 

 primitive type comparable to the immortal amoebae. 

 Here we have a most interesting case of senility and yet, 

 only local cerebral senility in a captive creature. It is a 

 supplement to what we have already noticed in connection 

 with the brains of bees. 



After this illustration, intended to bring out the contrast 

 between normal senescence with relatively trivial changes 

 and senility with marked degeneration or involution of 

 important structures, we venture to submit four theses, 

 that few wild animals of great age show any senile degenera- 

 tion ; that few wild animals of great age show more than 

 signs of general senescence ; that many very old men show 

 no signs of senility, but only of senescence ; and that, as all 

 the so-called signs of human senility may be found illus- 



