De Zouche. — Bacteria and their Belation to Disease. 37 



could hardly have been the true microbes of cholera, but the 

 idea of a vegetable parasite was there. In 1840 Henle pub- 

 lished a remarkable paper, " On Contagion and Miasma, and 

 Miasmatic Contagious Diseases," in which he " concluded, 

 from theoretical grounds, that contagious diseases must be 

 caused by organized contagia, which he considered were pro- 

 bably of the nature of low vegetable organisms. He further 

 added that these parasites need not necessarily be so small 

 that the magnifying-power of our microscopes was not suffi- 

 cient to demonstrate them, but perhaps they escaped obser- 

 vation only because of the difficulty of distinguishing them 

 from the surrounding tissues — a supposition which has been 

 brilliantly confirmed by the discovery of the tubercle-bacillus." 

 — (Fehleisen.) This was the real beginning of the bacterial or 

 ferment theory of disease. As already stated, however, the 

 origin of fevers de novo was maintained by some as late as 

 thirty years after this, and the extraordinary sporadic occur- 

 rence of fevers under circumstances which appeared to pre- 

 clude the possibility of infection in the usual sense seemed to 

 lend confirmation to this view. 



Before the theories started by Henle were entertained, the 

 W'Ord "parasite," in connection with disease affecting the human 

 species, was understood to ajjply to distinctly animal organisms, 

 such as entozoa ; later the term was extended to the fungi of 

 certain diseases of the skin and. hair, such as ringworm. 

 The word " fermentation" had long been in use to denote the 

 febrile process. What was called the effervescence or ebulli- 

 tion of the blood, by which terms the older physicians cha- 

 racterized its condition during the continuance of the high 

 temperatm-e in fevers, before the crisis, was believed to present 

 some analogy with the process of fermentation in vnious or 

 malt liquors, although the exact nature of alcoholic fermenta- 

 tion was still known to or suspected by but few. In 1842 

 Dr. Wilham Farr hitroduced the word " zymotic " to designate 

 the poison of specific fevers ; but he did not consider the 

 febrile process to be absolutely identical with ordinary fer- 

 mentation, and even then it was held that the ferment-pro- 

 ducing body was or might be some nitrogenous organic 

 substance without more exact definition. While physicians 

 were seeking for the poison of fevers, chemists were endeavour- 

 ing to discover the cause of alcoholic fermentation. The 

 vegetable nature of ferments was ascertained and asserted by 

 Cagnard de Latour in 1837, but the fact had not obtained 

 acceptance by the scientific world. The theory that ferments 

 were due to an organized body was definitely settled by the 

 researches of M. Pasteur (1857-60), who, in 1857, described 

 the little globules or short segments of the ferment of lactic 

 acid, and in 1858 those of alcoholic fermentation, and came 



