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the ‘Quarterly Review,'1 and still more lately in the 'Fortnightly Review,"? admirable résumés are given of what is known and has been supposed with regard to this possibility of human life-a subject to which the term 'longevity' has had its meaning narrowed, but one which will here be treated subordinately. It will be unnecessary therefore to refer further to authorities on this question, until their opinions are discussed. Naturalists and philosophers, including Aristotle, Bacon, and Haller, have incidentally given expression to opinion as to the causes of the varied tenure of life of organisms; but naturally the later writers have had a larger number of facts to deal with, and have been able to bring a sounder scientific knowledge to bear on the problem than those who preceded them. The treatise of Bacon, entitled 'Historia Vitæ et Mortis,' contains a most admirable enquiry into the causes of longevity. The question is attacked from every side, and the most ingenious hypotheses, with regard to animals and men, are suggested and discussed with that order and precision which belong to the great philosopher. At the same time, it must be admitted that, in Bacon's time, strange traditions and superstitions held men's minds, and that he actually, who shewed the means

1

January, 1868. Also see Sir Henry Holland's able Essay on * Human Longevity' in the 'Edinburgh Review,' 1857, hereafter referred to again.

? April, 1869.

by which we have become free from such impediments, was to a considerable extent affected in this way. The account of the ages attained by various species of birds and animals, given by Bacon, is very extensive, and his remarks upon each case valuable. These are referred to hereafter ; but his statements with regard to various cases of human longevity are less trustworthy, as well as his discussion of the value of inunction, of smelling fresh earth on waking, and other curious devices for prolonging life : little reliance, moreover, can be placed on the strange connections between longevity and personal qualities and characteristics, such as hairiness and temper, which Bacon enumerates. This treatise, however, is well worth the study of those interested in the subject, if only as a collection of strange fancies. Bacon's conclusions set forth in the thirty-two canons at the close of his treatise, explain variations in longevity as due to variations in the density of the 'vital spirits,' and other causes affecting these spirits. The work of the Prussian physician, C. F. Hufeland, entitled “The Art of Prolonging the Life of Man,' published in the beginning of this century, is to a great extent founded on Bacon's work, from whom most of his facts are derived. The advance in science during a century and a half, enabled him to treat the subject in a less metaphysical style than Bacon could ; at the same time, his philosophy is one which has now in its turn become antiquated. Hufeland endeavours, by an examination of the various leases of life in the vegetable and animal world and their connected conditions, to discover what will favour and what will combat the prolongation of life in man; and the latter part of his work is a recommendation of temperance and regularity in the exercise of the various functions, such being the lesson derived from his general study. At the outset of his enquiry Hufeland observes, "Is it then impossible to penetrate the intimate nature of this sacred flame (life), and to learn to distinguish what will feed it from what will diminish it ? I know how rash is the enterprise I have undertaken. I am about to approach a sanctuary from which so many presumptuous men have had to depart abashed and confused, and of which Haller himself, the favoured confidant of Nature, has said that no mortal can penetrate therein.' Hufeland had no cause to regret his enterprise, for though he did not accomplish his task, which indeed he could not hope to do, he has shewn an excellent path, which it remains for others to improve and extend.

The general conclusions Hufeland arrived at are as follows. He says, 'The duration of life depends then, in general, on the following circumstances. Ist. It depends on the quantity of vital force contained in the body. ... 2nd. Life consumes and destroys not only vital force, but also the organs; the destruction of life ought then to occur later in a body endowed with vigorous organs than in one in which the organs are delicate. . . . Thus, a certain solidity of general organisation and a suitable condition of the vital organs are the second condition on which length of life depends. 3rd. The consumption of vital force and of organs) may be more or less rapid, consequently its duration, or, what amounts to the same thing, that of life, may be, other things being equal as regards forces and organs, shorter or longer, according as the act of destruction operates with more or less intensity. 4th. Finally, since the reparation of losses is the principal means of counteracting consumption, a body which has the most perfect means of regeneration, both internal and external, will endure a longer time than one not provided with these means. In a word, the duration of life in a being depends on the sum of the vital forces which it possesses, on the greater or less consistence of its organs, on the rapidity or the slowness of its consumption, and on the perfection or imperfection of regeneration.'1

The only criticisms on these views which it is at present useful to make, is that they involve certain ideas which have become modified with the advance of science, and hence require to be adapted to present knowledge. In the sequel it will be seen how far they differ or agree with modern conclusions.

1 Hufeland observes in one passage, •The more imperfect the organisation the longer the life,' after describing the prolongation of life in plants by pruning. His own facts are sufficient to refute this as a general law. The truth is the very opposite of this.

A second work on Longevity, which treats of the general subject, and which therefore has an interest for the present enquiry, is that of the late P. Flourens, who was perpetual secretary to the Academy of Sciences of Paris, and Professor of Comparative Physiology at the Museum of Natural History: Flourens' work is devoted to human longevity in its first part, and in this connection he considers the longevity of other mammalia in order to answer this question, Is there any sure characteristic in animals from which we may infer their length of life? He gives the supposed age of several mammals, and the age at which the epiphyses of their bones are supposed to become united throughout the skeleton, and from this comparison he comes to the conclusion that in mammals and man the period of life is five times that of the period of growth,—a very neat and valuable rule to aid us in examining the question of the causes of longevity, were there a real foundation for it in fact. The data used by M. Flourens are, however, very few and of small credibility, whilst such as they are, they do not bear out his law of an exact quintuple ratio. The suggestion of fixing by the junction of the osseous epiphyses the period of growth, is nevertheless one of great practical value.

In a work entitled, 'Life, its Nature, Varieties and

· Buffon had previously supposed a ratio of 7 to 1 as that of the length of life to length of growth.

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