468 DR. p. CHALMERS MITCHELL ON LONGEVITY AND 



In the meantime, however, it is possible to gain considerable 

 information, at least of a comparative kind, fiom such records as 

 I had at my disposal. 



Uncertainty of age and varying conditions of health on arrival, 

 arid the abnormal conditions during detention, make it doubtful 

 if the maximum durations at the Gardens give very reliable 

 evidence as to the potential longevities of the species concerned. 

 The following conclusions, however, have some foundation, at 

 least if taken relatively. Amongst Primates, the Anthropoids 

 have a lower potential longevity than man, and longevity 

 decreases gradually towards the smallest monkeys, whilst in the 

 case of Lemurs it rises considerably. The potential longevity of 

 Carnivora is relatively high, and wherever the conditions are 

 reasonably favourable, cases of long life in proportion to size are 

 abundant. Insectivora have low potential longevity. Rodents 

 have an unexpectedly high potential longevity, there being many 

 cases of unusually great age, in proportion to size. Elephants 

 and the larger Ungulates have low potential longevities in pro- 

 portion to their size ; all Ruminants have a i-elatively low 

 potential longevity, and the correlation with size is absent, or 

 almost reversed ; in proportion to their size, many of the smaller 

 forms, such as Sheep and Goats, are much longer lived than 

 Giraffes, Elands, or Cattle. Edentates supply a number of 

 examples pointing to a high potential longevity; whilst Marsupials 

 generally, with exceptions, such as Wombats and Phalangers, 

 have a relatively low potential longevity. 



Metchnikoff has elaborated the view that a chief cause of 

 senility is auto-intoxication from intestinal putrefaction, and 

 that, on the whole, those animals v/ith the most capacious cseca, 

 large intestines and rectums, have the shortest lives in proportion 

 to their size and organization. The inferences from the maximum 

 and average durations recorded here, are in general agreement 

 with this view ; the number of instances of animals and groups 

 of animals with relatively capacious hind-guts and short and 

 fragile lives being very great. The most notable exceptions are 

 some of the Rodents, for instance Squirrels and Porcupines, and 

 some of the Marsupials, such as Wombats and Phalangers, which, 

 although they have relatively capacious hind-guts, have relatively 

 high viability and longevity. It must be noted, however, that if 

 the data were such as to exclude the unfavourable effect of the 

 special conditions in captivity, these exceptions might disappear. 

 I think the general proposition is true, that in proportion to 

 its size, an animal with a short hind-gut is hardier and has an 

 expectation of longer life. 



The most important inference that I draw from these records 

 is the complete failure in practice of the theory that protection 

 from cold by artificial heat is the fundamental requisite for 

 mammals in captivity. In the long list of mammals, belonging to 

 nearly every group, and coming from every part of the world, 

 there is no case of the successful application of this method, that 



