MUCOUS MEMBRANE OF THE TONGUE AND NOSE. 239 



coverer, Pacini. Similar bodies are also found in the organs 

 of the sexual sense, in the penis of the male and in the 

 clitoris of the female ; these are processes of the integument, 

 and the development of which we shall consider presently, 

 in connection with that of the other organs of generation. 

 The development of the organ of taste, the tongue and the 

 palate, we will also consider presently, in connection with 

 that of the intestinal canal, to which these parts belong. 

 To one point, however, I will now call particular attention, 

 viz., the mucous membrane of the tongue and palate, in 

 which the taste-nerve terminates, is also in its origin a portion 

 of the external skin-covering. For, as We found, the entire 

 mouth-cavity originates, not as a part of the actual intes- 

 tinal canal, but as a groove-like inversion of the external 

 skin (vol. i. p. 338). Its mucous membrane, therefore, is 

 formed, not from the intestinal layer, but from the skin- 

 layer, and the taste-cells on the upper surface of the tongue 

 and palate arise, not from the intestinal-glandular layer, 

 but from the skin-sensory layer. 



This is equally true of the mucous membrane of the 

 organ of smell, the nose. The history of the development 

 of this sense-organ is, however, of far higher interest. 

 Although the human rose, externally viewed, seems simple 

 and single, yet in Man, as in all higher Vertebrates, it 

 consists of two perfectly distinct halves, of a right and a left 

 nasal cavity. These two cavities are entirely separated by 

 a vertical partition, so that the passage into the right nasal 

 cavity lies only, through the right nostril, and into the left 

 cavity only through the left nostril. Posteriorly the two 

 nasal cavities open separately through the two posterior 



nasal apertures into the head of the pharynx, so that the 

 49 



