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INTRODUCTION. 



age alone, that the exact period of the duration of life, even in those which 

 man has domesticated, is not, in all cases, to be precisely ascertained. 

 Our data cannot be safely taken from single instances ; a collection of 

 examples is requisite : to carry out the necessary researches, through 

 the Mammalia alone, involves the labour of years, and will lead, at 

 last, only to general deductions. Something may be learned from the 

 extensive vivaria, which the rising taste for natural history has established 

 in so many parts of Europe ; but, unfortunately, animals in confine- 

 ment seldom reach maturity ; for, from the privation of liberty, the re- 

 striction of their bodily exercise, the unnatural food upon which they 

 often subsist, and from an impure atmosphere, and an uncongenial climate, 

 even should acute disease not sweep them off, their enfeebled constitution 

 sinks, by slow decay, and prematurely yields to death. 



Hitherto, then, the little knowledge which we possess, respecting the 

 natural duration of the life of animals, appears to be more the result of casual 

 opportunities than of systematic observation. Events, apparently acci- 

 dental, have sometimes furnished us with facts, which diligence could not, 

 perhaps, have ascertained. It is not, however, to be supposed, that every 

 fact which has been, from time to time, observed by various individuals, 

 has been duly placed on record ; many have been lost, because their im- 

 portance has not been known ; and many others have not yet found their 

 way into the archives of science. It is, generally, considered as a rule, that 

 the sooner an animal arrives at maturity, the sooner is its existence ter- 

 minated ; and, without doubt, a certain degree of truth attaches to this 

 opinion ; more especially on a broad comparison of the vertebrate classes 

 among each other. A question, however, here opens : what are we to 

 understand by maturity ? The maturity of Mammalia supposes the com- 

 pletion of growth, and the power of reproduction ; so, also, among birds ; 

 not so among reptiles and fishes, for these reproduce their species long 

 before the period at which their growth is stationary. The term, matu- 

 rity, therefore, in the sense in which we apply it to Mammalia and 

 birds, is not appropriate to these. Indeed, among the cold-blooded Ver- 

 tebrata, whose circulation is languid, whose natural heat is not much 

 above that of the medium in which they live, and whose tenacity of 

 life is proverbial, the natural duration of their existence might be sup- 

 posed to be considerable. Tortoises and Turtles drag on a life through 

 ages. In the Bishop's garden, at Peterborough, a Tortoise died in 1821, 

 which must have exceeded 220 years of age. The Lambeth Tortoise, 

 which was introduced into the garden in the time of Archbishop Laud, 

 about the year 1625, died, from some neglect on the part of the gar- 

 dener, in 1753 ; having been in the garden 128 years. Gilbert White 

 records several details respecting a Tortoise which had lived thirty 

 years in captivity ; and states, that another, in an adjacent village, " was 



