480 Dynamic Theory. 



of it to enter another state in which it is called ozone. In this condition 

 its molecule is composed of three atoms, and is necessarily of a different 

 shape, and in this condition it can be smelled, the odor being similar to 

 that of sulphur. It is therefore established that in this case the shape 

 of the molecule alone determines the potentiality of the substance to 

 agitate the pituitary cells. In the other cases as no difference can be 

 detected or suspected in their molecules except difference of shape, it 

 seems reasonable to conclude that the shape alone of each molecule in- 

 volves the quality which is characteristic of its odor. 



Sometimes one odor is able to neutralize or disguise another. This is 

 doubtless due sometimes to the chemical action of the two odors upon 

 each other and the mucous fluid of the pituitary membrane, the triple 

 action resulting in a molecule differing from one which might be formed 

 by the action of any two of the three. At other times each odorous 

 body might make its separate impression on the brain cells ; but one of 

 them of such overpowering intensity as to cause a greater erection of the 

 brain cells affected by it, and consequently to arouse consciousness ex- 

 clusively towards it ; just as a person suffering a great pain from one 

 part of the body may be quite oblivious to a little one coming from 

 another part. A game-keeper once apologized for the failure of his 

 hounds to follow the game by declaring that the scent was overpowered 

 by ' them stinking violets. " ( Punch. ) 



CHAPTER L. 



TASTE. 



The organ of taste consists of a portion of the outer skin, which dur- 

 ing the development of every individual is inverted or invaginated by 

 being pushed in from the outside, as it were, during the formation of the 

 mouth. It is therefore simply a specialized or differentiated portion of 

 some of that part of the external skin which after becoming internal is 

 called epithelium. In the case of this organ, and that of smell, there is 

 no detachment or break in the continuity between the outside skin and 

 the epithelium, but they grade one into the other. In the case of the 

 eye and ear organs, they too are equally differentiated from the outside 

 skin, but in the course of their evolution they have finally become de- 

 tached from it and are no longer continuous with it, but are isolated sacs. 



The tongue is the principal organ of taste. It is covered with the 

 same epithelium which lines the cavity of the mouth, and the cavities 

 mentioned in last chapter in connection with the sense of smell. The 

 tongue is an organ exposed to a very large amount of stimulation and 



