AN ESSA Y ON LONGEVITY. 



by which we have become free from such impedi- 

 ments, 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 re- 

 liance, moreover, can be placed on the strange con- 

 nections 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 con- 

 clusions 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 be- 

 ginning 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 



