AIDS TO THE STUDY OF PHARMACOGNOSY. 
The consideration of medicinal substances in their various 
aspects, as has been indicated, presupposes the possession of 
corresponding adjuncts or aids. These are primarily the requi- 
site preliminary knowledge of botany, zoology and chemistry, 
as also experience in the use of the microscope. With this 
general knowledge, and the corresponding degree of skill, phar- 
macognostical description is everywhere intimately connected, 
as well as with the practice of pharmacy itself. The present 
work has not included the chemistry of plants in its plan, 
nor is it designed as a complete guide for microscopical study, 
and refers, therefore, in this respect to the literary aids enu- 
merated under section II., B, page 4%. In addition to the 
latter, an oral and practical introduction to the methods of 
microscopical examination is expressly recommended. Such 
opportunities are easily obtained, and, as in other departments 
of applied natural science, practical instruction proves here also 
to be of the greatest utility. Those who earnestly enter this 
field will soon become incited to zealous labor. 
As scientific aids the following are to be considered: 
I. COLLECTIONS. 
A. Collections of Drugs.—The pharmacies themselves rep- 
resent to a certain degree such collections, which are found more 
complete, in their adaptation to scientific purposes, in many of 
the higher educational institutions, and particularly in such 
as are directly subservient to the interests of pharmacy. 
The most instructive, and by far the most extensive collection 
. 
