AND COMPARATIVE ANATOMY. 43 



parts, generally in an imperfect state, or, in the anatomical 

 phrase, as rudiments, in some animals, where the function 

 does not exist, and where the parts therefore are not em- 

 ployed. It seems as if a certain model or original type? 

 adapted to the intended function, had been fixed on as a 

 pattern for the construction of nearly allied and analogous 

 beings ; and tiiat this model had been adhered to, even in 

 those cases where some particular function did not exist, 

 and where, consequently, tlie corresponding organ was in 

 reality unnecessary. The additional pelvic bones, which 

 support the false belly or abdominal pouch of tlie marsupial 

 animals, are found in the males as well as in the females ; 

 although the former have not the pouch. Several carni- 

 vorous animals have clavicular bones, connected merely to 

 the muscles, and obviously incapable of serving, even in 

 the smallest degree, those purposes for which true clavicles 

 are added to the skeleton. The breasts and nipples of male 

 animals are another example. 



The marsupial bones and the milk-secreting apparatus of 

 female animals are appointments of organization manifestly 

 designed to fulfil certain ends, and accomplishing very es- 

 sential purposes in the economy. In the male sex they 

 are neither subservient to use nor ornament ^ and seem, to 

 our imperfect knowledge, to exemplify the prevalence, in 

 animal organization, of a mechanical principle, of the ad- 

 herence to a certain original type or model. 



The olfactory nerves of the cetacea, in whom the blow- 

 ing holes occupy the place of the nose, afford another in- 

 stance — the more remarkable, as their existence has been 

 generally denied, even by the greatest authorities in com- 

 parative anEitomy. They consist in the porpoise of two 

 white extremely slender filaments, which, although visible 

 to the naked eye,, cannot be distinctly recognized as nerves 

 without a magnifying-glass*. 



* Treviranus, Biologic, b. v. p. 342, tab. 4. 



Blainville and Jacobson had already asserted the existence of olfactory 

 nerves in the cetacea in the Bulletin des Sciences, 1815, p. 195. 



In the work quoted above, Treviranus describes a very singular devia- 



