268 



SCIENCE 



[N. S. Vol. XXXVI. No. 922 



years to come to a knowledge of the truth re- 

 garding the cause and manner of spreading 

 of plague, to a knowledge of that chain of 

 cause and effect which connects microbe and 

 man in the dire relationship of the plague- 

 stricken. 



Science, then, has come face to face with 

 the specter of the Black Death and recognized 

 its features. She has laid hold of "the pesti- 

 lence that walketh in darkness " and made it 

 reveal its horrid origin. 



Similarly for influenza, a disease in its epi- 

 demic form, if not quite so deadly as plague, 

 then quite as mysterious ; in some forms quite 

 as deadly. Very probably some of the great 

 epidemics of the middle ages were in reality 

 what we now call influenza, its very name 

 being only the Italian for influence — a some- 

 thing inscrutable but omnipresent, mysterious 

 in the last degree. The usual expressions 

 were in vogue, it was a corruption in the air, 

 a miasm, an exhalation and so on; until in 

 1892 the bacteriologist Pfeiffer isolated the 

 organism of influenza and named it the Ba- 

 cillus Influenzm. Not the air, then, but the 

 microscopic fungi it may hold for evil influ- 

 ence, is the true cause of influenza. The in- 

 fluence is now materialized, nay indeed is iso- 

 lated and sealed down under glass for the in- 

 spection of trained eyes. Thus by the micro- 

 scope are these deadly powers of the air one 

 by one distinguished from each other and 

 identified each in its particular malignancy. 



No better example than that of the ferments 

 could be given of a notion becoming in course 

 of time a substance isolated and tangible. 

 Fermentation, the totality of changes pro- 

 duced in digestible, coagulable or putrescible 

 material, was for ages believed to be inscrut- 

 ably mysterious. It was made the subject of 

 debate between the iatro-mathematicians and 

 the iatro-chemists of the seventeenth century, 

 but neither school really understood it. 



Digestion, the great fermentative process in 

 animals, was confused not only with putre- 

 faction, but with boiling and with the effer- 

 vesence of gas in chemical operations. 

 Stahl saw in digestion the direct activity of 

 the soul or anima which, he held, permeated 



every tissue and endowed it with its special 

 powers. The chemistry of it all, however, was 

 unknown : the very conception of a ferment — 

 a substance produced by living matter but not 

 itself living — had not as yet emerged from the 

 mental confusion. 



Van Helmont (15Y7-1644), Sylvius (1614r- 

 1672), De Graaf (1641-1672), Haller (1708- 

 1777), all groped for it, but it was not until 

 through the work of Eene Antoine Ferehault 

 de Eeamur (1750) that any true idea was held 

 as to the nature of fermentation in digestion. 

 Eeamur was the first to obtain gastric juice 

 in an approximately pure state and to attempt 

 digestion with it outside the body. Spallan- 

 zani, the distinguished Italian naturalist at 

 Pavia, began where Eeamur left off, and soon 

 discovered that digestion was by no means 

 putrefactive but was apparently due to some 

 " solvent power " or " active principle of solu- 

 tion " in the gastric juice (1777). Then by 

 degrees as physiological chemistry improved 

 its methods, it got finer results, and at last 

 " the solvent power " or " principle of solu- 

 tion " in the gastric juice was isolated in 1862 

 as the white powder, pepsin, a name which had 

 been given to the active principle by Schwann 

 as far back as 1836. Soon other ferments 

 were either isolated or obtained in solution, 

 and to-day in our laboratories we store in 

 glass bottles half a dozen or more of the ac- 

 tual substances which are the modern repre- 

 sentatives of the " principles of solution " of 

 the early researchers. The vague has become 

 definite, the conceptual power or property has 

 become the material substance or entity. 



The story of the discovery of the telescope, 

 how it was bound up with that wonderful 

 emancipation of the human spirit from the 

 thraldom of mediaeval ignorance and the hatred 

 of scientific light, has been told us by many 

 learned men; but I venture to think that the 

 discovery of the microscope, which has never 

 yet had its historian or poet, was one fraught 

 with many more beneficent results for human- 

 ity. By its scrutiny the invisible but actual 

 sources of most of the scourges of mankind 

 have been discovered; and it would seem that 

 it is in its power and not in that of fleets or 



