238 



THE EVOLUTION OF MAN. 



Three Groups. 



Sense-organs. 



Sense-nerves. 



Sense-functions. 



r I. Skin-covering 



A. Sense-organs in 

 which the ter- 

 minal expansions 

 of the nerves are< 

 distributed in the 

 outer skin-cover, 

 ing. 



B. Sense-organs in 

 which the ter- 

 minal expansions 

 of the nerves are 

 distributed over 

 inverted grooves 

 of the outer skin- 

 covering. 1^ 



C. Sense-organs in 

 which the ter- 

 minal expansions 

 of the nerves are 

 distribute! over^ 

 vesicles sepa- 

 rated from the 

 external skin- 

 covering. 



(outer skin, or 

 epidermis, and 

 leather - skin, 

 or coriuvi) 

 II. External 

 sexual parts 

 (pents and cli- 

 toris) 



III. Muconsmem- 

 brane of the 

 mouth - cavity 

 (tongue and 

 palate) 



IV. Mucous mem- 

 brane of the 

 nose-cavity 



V. Eye 

 VI. Ear 



I. Skin nerves ■. Sense of pressure 

 (tiervi cufanei) I Sense of warmth 



II. Sexual nerves 3. Sexual sense 

 (^nervi pudendi) 



III. Taste nerve 4. Sense of taste 

 {nervus glosso- 

 pharijngmis) 



IV. Olfactory 5. Sense of smell 



nerve 

 (n. olfactorius) 



V. Sight nerve 6. Sense of sight 

 (n. opticus) 



VI. Ear-nerve V. Sense of hear- 

 (n. acousticus) ing 



Of the developmental history of the lower organs of 

 sense I have but little to say. The development of the skin- 

 covering, which is the organ of the sense of pressure (sense 

 of touch) and of warmth, we have already traced (p. 209). 

 I need only add that in the leather skin (corium) of Man, 

 as of aU higher Vertebrates, innumerable microscopic sense- 

 organs develop, the direct relations of which to the sensa- 

 tions of pressure or resistance, of warmth and of cold, are 

 not yet ascertained. These organs, in or upon which the 

 sensitive skin-nerves terminate, are the so-called "touch 

 bodies " and the " Pacinian bodies," named after their dis- 



