222 MANTON COPELAND 
stimuli were obtained while isolating the responses initiated by 
olfactory stimuli and localizing the organ of smell. Some of 
these should be briefly reviewed here. 
As Parker and Stabler (’13) have emphasized in a paper on 
taste and smell, the distinction between the two senses which is 
most widely applicable is a quantitative one. Olfactory organs 
are stimulated by relatively weak solutions and gustatory organs 
only by relatively strong ones. Consequently, when an animal 
possessing organs of taste and smell encounters a relatively 
strong food substance, reactions may occur which, under certain 
circumstances, represent the combined effects of both gustatory 
and olfactory stimulations. When, however, this substance is 
sufficiently diluted, a concentration of the stimulating material 
is obtained which does not affect the gustatory organs, and re- 
actions which it then calls forth are recognizable as olfactory, 
and the organ stimulated as an olfactory receptor. Since, for 
example, snails which show easily detectable responses to dilute 
food materials fail to show them after the osphradium is de- 
stroyed, when it is clear that other factors are not influencing 
the results, the conclusion drawn is that the osphradium is an 
olfactory receptor. It is equally evident that after the organs 
of smell have been rendered non-functional, reactions isolated 
from olfactory ones may be initiated with relatively strong 
stimulating materials derived from food, and the receptive areas 
localized. Working, therefore, upon this quantitative basis of 
distinction between the two senses, the reactions of the snails 
to food or its derived stimulating juices, as well as the receptive 
surfaces concerned with them can be determined as olfactory 
or gustatory. 
It is recognized that confusion may arise between taste and 
the common chemical sense for the reason that relatively strong 
solutions may stimulate the endings of nerves associated with 
the latter, as has been demonstrated in a number of vertebrates 
where the nature of the nerve terminations concerned with the 
two senses is, better known. Since, however, the materials used 
in stimulating the snails were food and its juices, and reactions 
occurred which were distinctly positive in character or which 
