76 EX VIRIBUS VIVIMUS. 



for example, in personal expenditure and degree of 

 evolution. One ought to compare organisms which 

 are alike in these two last quantities. In trees, we 

 may take the pear, apple, and such fruit-trees, and 

 we find that they are excessive in their reproductive 

 expenditure, and short-lived as compared with other 

 trees which agree (as do all Vegetals) in the absence 

 of personal expenditure, and are of equivalent indi- 

 viduation. In animals^ we may best compare expe- 

 rimental cases : thus we find that animals used for 

 breeding, and made to breed early, are less long- 

 lived than those which are not so used.^ There are, 

 besides, two important cases to compare, viz. mules 

 which are born incapable of reproducing, and animals 

 which have been operated upon. With regard to the 

 Mule, Bacon states that it lives longer than either 

 the Horse or the Ass, which confirms the hypothesis 

 that generative expenditure antagonizes longevity. 

 But as to the results of operations, it appears that, 

 as in cases of forced abstinence, a disturbing element 

 is introduced by the interference with the proper 

 functions and nutrition of the animal. The principle 

 of Treviranus, 'that every organ is as an excreting 

 gland to the rest of the body' must be remem- 



' The case of Actinia is alluded to farther on. Its longevity is an 

 example where small generative expenditure, either asexual or sexual, 

 entails long duration of the individual. 



'^ This statement is derived from general assertions and needs con- 

 firmation. 



