254 Early Studies in Bacterial Plant Diseases 



zealous to learn of them, both from the available scientific litera- 

 ture and his own laboratory research, cannot be doubted. Every 

 bio-chemical laboratory technician and ardent follower of Louis 

 Pasteur watched in America with eager restlessness the accumu- 

 lating scientific progress being achieved by his disciples in the 

 Pasteur Institute and other of the great laboratories of Europe. 

 In 1877 Emile Duclaux had begun to assemble within the compass 

 of some pages for Dr. Dechambre's Dictionnaire des sciences 

 medicales a coordinated body of learning from scattered facts 

 concerning the enzymes.** In 1882 had appeared Duclaux's ¥er- 

 ments et Maladies, and in 1886 his Le Microbe et la Maladie. 

 We cannot affirm with certainty that Smith by the years 1893-1894 

 had studied these volumes. Most assuredly within a few years 

 he was acquainted with the work of Duclaux, and by the year 

 1894 had familiarized himself with the views of the German 

 Oskar Loew. 



Among scientists, the view then, as now, was that certain of 

 the ferments of fungi and bacteria are enzymes. Throughout the 

 rest of the century. Smith, when describing a bacterial disease of 

 plants, listed the factor of enzymes among the fermentation pro- 

 ducts of the causal microorganism. Enzymes were believed to have 

 been isolated from a number of bacteria, and Smith now so stated 

 in his review of Green's paper. " Vegetable ferments," he said, 



are readily destroyed by boiling, and are for the most part very sensitive 

 to acids and alkalies, a slight excess destroying them or stopping all action. 

 They are not readily identified in tissues by use of stains. Some are very 

 unstable. Enzymes have very slight power of diffusion. They can make 

 their way through cell walls, but not through the parchment walls of 

 dializers. They appear to act in an ordinary chemical way, causing hydra- 

 tion (myrosin excepted) and subsequent decomposition. Most of the 

 changes brought about by enzymes can be effected in the laboratory by 

 ordinary chemical processes. They are extracted for experimental purposes 

 by water, salt water, or glycerine, and are quickly precipitated by excess of 

 alcohol. One of their most striking peculiarities is the enormous power of 

 conversion they possess, a sample of invertase (which occurs in a variety 

 of vegetable substances, — yeast, bacteria, fungi, malt, buds and leaves, 

 pollen, grains, etc.) being capable of inverting 100,000 times its own 

 weight of cane sugar without injury to itself. The ferments of the fungi 

 and bacteria are also enzymes, and the old view of Naegeli that there are 



** Erwin Frink Smith, Introduction, Pasleur, The History of a Mind, by Duclaux, 

 and translated by Smith and Florence Hedges, pp. xvii, xv and xvi. 



