EX VIRIBUS VIVIMUS. 



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. Flou- 

 rens, 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 mam- 

 mals, 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 sug- 

 gestion 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 i as that of the 

 length of life to length of growth. 



