ANALOGIES AND AIjEINITIES. 41 



principles. That certain vegetable products taken internally 

 produce emesis, argues little for the identity of eheniical 

 principle in all vegetable emetics, and perhaps less for the 

 consanguinity of the plants which yield them, other consider- 

 ations being left out of view. Notwithstanding this last con- 

 cession, the first proposition holds good, tliat a common 

 medical property w^ill often run through all the hundred or 

 thousand species of a large family of plants. Such a property 

 is doubtless good evidence of the recognized common affinit}^, 

 in such a case ; while its recurrence elsewhere may be of 

 analogy only, or it may indicate a real affinity which might 

 or might not otherwise have been suspected, between families 

 or genera. In view of this kind of possibility, it seems as if 

 there might be at least the chance of some improvement in 

 the system of botanical classification, by giving more atten- 

 tion to the properties of plants in relation to their affinities. 



The therapeutic aspect of the subject may here be dis- 

 missed, in favor of what I assume to be a more general and 

 at tlie same time a more delicate, and, to botanists an 

 equally satisfactory test of the qualities of plants. 



Some months ago, a botanical friend remarked to me 

 what I had often before reflected on— that it seemed strange 



r ^^ 



men should never make use of any otlier sense tlian tliat of 

 vision in botanical diagnosis. Why should we not emiiloy 

 more freely and more trustingly our tasting and smelling 

 faculties along these lines of investigation ? By means of 

 these two senses men do lay liold securely on many a fact 

 which completely eludes their keenest visual search, even 

 when aided by the best microscopes. As tests of the presence 

 of certain qualities in plants— whether therapeutic or not it 

 matters not— these two senses are far more delicate than are 

 those organs by which the results of therapeutical activity 



are manifested. 



One reason why botanical authors in general make so little 

 of the odors and flavors of plants is, that in the Jiorfus siccus 

 these qualities do not appeal to them. For another, we may 

 advert to the weight which certain scientific precepts vener- 



