Animal Morphology. 119 



teeth are not exceptional, but they contain within them the 

 conditions of a serous and mucous membrane, or bony and 

 enamel substances, etc. 



It will be said that, in ordinary serous membrane, we have 

 no ground for supposing it ever assumes a truly fine segmen- 

 tation, so as to form hair, etc. But even here we have in 

 the lining membrane of the ampullae of the semicircular 

 canals of the ear fine hair-like processes, which membrane 

 is essentially a serous one.* 



But membrane in morphology, from its very metamorphic 

 changes in cell differentiation, must alter in its form and 

 structure ; but in its function it will always possess in every 

 membrane the essential type in relation to the rest namely, 

 physical and mechanical convenience without either con- 

 tractile or active vital function. It is even doubtful 

 whether serous membrane could on its own surface form 

 a true ulcer, like to bone and mucous membrane, on account 

 of its peculiar vital endowments, though apparently so 

 highly organized in man, as in the pleura and peri- 

 toneum. 



It has been already remarked that nerves of force are 

 distributed on the integument in certain parts, as in the 

 bend of joints, the palms of the hands and soles of the feet, 

 along the mesian line of the lips, centre of the forehead, 

 the nipples, and between the fingers and toes. In all these 

 places, if water is applied, and then blown upon for a few 

 seconds, cold is very quickly felt.t 



Touch, on the other hand, is found at the lips and palate 

 generally, especially the tip of the tongue, and the pulp of 

 the teeth, the finest particles being recognized when pressed 

 between the teeth, and the tips of the fingers and toes. 



;: Vide Huxley's " Elementary Physiology," page 223. 1869. 



f Edinburgh Medical Journal for March, 1859 : " An Experimental 

 Inquiry into the Existence of a Sixth Sense." 



