LECTURE VI. 285 



dry into a crust, as mucus does, nor to 

 become rancid and acrid, like oil. Its bit- 

 terness, they say, also renders it disgusting 

 to insects, which might in our sleep seek 

 to nestle in that passage. The necessity 

 for the lining of the tube of the ear being 

 kept constantly moist is evident, for when 

 the cerumen is deficient in quantity, or 

 faulty in quality, then the oscillations of 

 sound, or the pulsation of the vessels, pro- 

 duce vibrations in the tube, causing noises, 

 which patients compare to the rustling of 

 leaves, or the gushing of waters, and the 

 beating of hammers. 



Though the exact structure of the cover- 

 ings of animals appears to be less accu- 

 rately known than that of most other parts, 

 yet from the general consideration of the 

 subject, I think we are warranted in con- 

 cluding, that Nature has either, from the 

 texture of the substances with which she 

 has invested them, or the qualities of those 

 with which they are besmeared, cut off all 

 communication between the interior of 

 living beings, and the elements in which 



