158 



THE OSPREY. 



nine iiiDiiths; tliat nf tlio eU-i)liaiit i^ iioiiiiy two 

 years, etc." 



Flourens ])iistiilates as a criterion of maturity 

 the union with the bones of their epiphyses. 



"As hiuf;- as the bones are not united to their 

 epii)hvses. tlu- animal g-rows; when once the 

 bones and their epiphyses are united, the animal 

 grows no more." In man this union is effected 

 "at twenty years of ag-e" says Flourens. 



The subject of mammalian long-evity has also 

 been the subject of discussion very recently in 

 Nature, for January S, March 23, and May 11. 

 A curve of life has been projected by Dr. 

 W. Ainslie HoUis (January 5.) correlating the 

 "years of adolescence" with the "years of poten- 

 tial longevity", and his conclusions are enun- 

 ciated in the proposition: The ratio of length 

 of adoleseence to length of life in the shortest 

 lived mammals is proportionately less than it 

 is in longer lived mammals". 



Mr. Ernest D. Bell (March 23) follows with 

 the proposition that "the full term of life in a 

 mammalian species is equal to ten and a half 

 times the period of maturity divided by the cube 

 root of the period (of maturity)" and gives a 

 mathematical formula embodying the proposi- 

 tion. Soon afterwards (May 111. he thought 

 the formula might be advantageously modified 

 by substituting 10.1 for 10.5, the full term of life 

 then being supposed to be "10.1 times the cubic 

 root of the square of the period." 



Dr. HoUis admits that the formula confirms 

 his opinion, and adds some cases of domestic 

 animals which "conform to the requirements of 

 the curve very closely". They are named below. 



Guinea-pig 



English Gre.vliound. 



C\it (Miviu-t) 



Cat (.leuuiuKs) 



Hog 



English Hunter 



Observed 

 length of 

 Ado 1 e - 

 scence. 



7 months. 

 1 year. 

 1 •■ 



B« ' 



Length ot Life. 



Observed 

 by curve. 



yrs 7 yi's 

 ., j2 .. 



■• 12 •• 

 ■■ IS •• 

 .. 3, .. 



" 35 •■ 



Computed 

 by form. 



7..f3 yrs. 

 la.'i ■■ 

 10..') •■ 

 16117 ■• 

 3(1.7 •• 

 35.C3 •• 



Dr. Hollis adds that "the age at which growth 

 ceases in man differs considerably in different 

 individuals of the same race". He had "in 

 skiagraphs observed a difference of upwards uf 

 three years in the ages of different subjects, at 

 which osseous union of the epiphyses to the 

 finger-bones was effected." Dr. Hollis thinks 

 that "the age of twenty-five years for man's ces- 

 sation of growth is therefore only an average 

 one", and in his revised curve he "reduced the 

 age of man from eighty to seventy-five years." 



The difference between Flourens and Dr. 

 Hollis in estimating the longevity of man of 

 course results from their difference of uieaniiig 

 as to longevity. Flourens meant potential 

 longevity; longevity very rarely obtained, and 

 only under exceptional circumstances. Dr. 

 Hollis restricted it to average or ordinary long- 

 evity. 



There is unquestionably a fallacy inherent in 

 all the "laws" or generalizations thus proposed: 

 tliat fallacy is the assumption that a rule which 

 holds good for some of a class must hold good 

 for all. There is no rea.son to suppo.se that any 

 one of the "laws" or rules is of universal appli- 

 cability for any single class — mammalian or 

 other; much less for all vertebrates. Neverthe- 

 less, the tendency among terrestrial placental 

 mammals apjjears to be decided and of great 

 interest. 



It is very desirable to kn<nv whether any such 

 relations of time as prevail for many terrestrial 

 mammals at least exist among- birds. Favorites 

 as they are, of so many lovers of nature, very 

 little tliat is exact is known respecting- the dura- 

 tion of tlieir life or tlie epochs of that life. 

 Flourens admitted his ignorance. "I know 

 notliing certain of the duration of life in birds," 

 says he. Others who knew less professed to 

 know more. Some of their speculations or as- 

 sumptions are summarized by Flourens. 



"Hesiod" says Pliny, "attributes to the rook 

 nine times our life; to the stag four times the 

 life of the rook; and three times the life of the 

 stag to the raven. Hesioihis cornici novem 

 nostras attribuit ietates. quadruplum ejus cervis, 

 id triplicatum corvis". 



"Buffon thus remarks upon this passage in 

 Pliny: In taking the age of a man at only thirty 

 years, this will give nine times thirty, or two 

 hundred and seventy years for the rook, one 

 thousand and eighty for the stag, and three 

 thousand two hinidred and forty for the raven. 



•'In reihiciiig- tile life of man to ten years, this 

 will give ninety years for the rook, three hun- 

 dred and sixty for the stag, and one thousand 

 and eig'^hty for the raven, which is still extrava- 

 gant. The only way to give a rational meaning 

 to this passage, is to render the gcnca of Hesiod, 

 and the atas of Pliny by years; then the life of 

 the rook is diminished to nine years, that of the 

 stag to thirty-six, and that of the raven to one 

 hundred and eighty, as is provided by observa- 

 tion". 



Buffon, adds Flourens, "is quite at liberty to 

 comment upon Hesiod and Pliny as he pleases, 

 but he ought, at least, to tell us upon what facts 



