138 Trans. Acad. Sci. of St. Louis. 



borrow a word. But the century just closed has seen a dif- 

 ferentiation of pharmacy from medicine which has not only 

 greatly simplified the materia medica through its more 

 careful investigation, but has given the physician more free- 

 dom to follow out his own field, so that to-day, while he must 

 know experimentally the physiological action of more plants 

 than his predecessors actually used, he need not ordinarily 

 know more of these plants thau that their active principles, in 

 sulphates, fluid extracts and the like are commercially pro- 

 curable in definite degrees of assimilability and concentration, 

 though his final trials have not been lessened thereby. 



The century will forever stand as that in the last third of 

 which the germ causation of disease was made known, and 

 the names of Pasteur, Koch and Lister are inseparably con- 

 nected with this great addition to knowledge, which, — since 

 the germs of disease are for the most part bacteria, that, 

 though of simple and aberrant structure, are commonly 

 classed with plants, — must be counted among the achieve- 

 ments of botany. Sanitation and surgery have both been put 

 on an entirely new footing by this recognition that the minut- 

 est organisms yet known are responsible for many of the most 

 dreaded pests, so that the exclusion or elimination of germs, 

 and the use of their own products, — either direct or by ani- 

 mal reaction in the form of serums, — in therapy, form to- 

 day the surest safeguard against infectious disease, the occur- 

 rence of which may soon be regarded as almost a stigma on 

 civilization. 



The century just closed has witnessed an almost equal ad- 

 vance in knowledge of the causation of the diseases of plants 

 themselves. Rusts, smuts and mildews are no longer looked 

 upon as exanthemata, but the fruits of parasitic fungi, which, 

 more than is the case with the parasites of animals, are of the 

 less minute and therefore more easily seen and controlled 

 groups, — though plants are also subject to a few bacterial 

 diseases. Much has been done in the way of prophylaxis, 

 and something in the way of germicide therapy, in this field, 

 and the foundations of a true science of plant pathology based 

 upon distorted physiological processes due to improper en- 

 vironment, food and the like, or to the ferments secreted by 



