FERMENTATION AND DISEASE. i 49 



ing out before the physiologist causes me to conclude that no greater 

 calamity could befall the human race than the stoppage of experi- 

 mental inquiry in this direction. A lady whose philanthropy has ren- 

 dered her illustrious said to me, some time ago, that science was be- 

 coming immoral; that the researches of the past, unlike those of the 

 present, were carried on without cruelty. I replied to her that the 

 science of Kepler and Newton, to which she referred, dealt with the 

 laws and phenomena of inorganic Nature ; but that one great advance 

 made by modern science was in the direction of biology, or the sci- 

 ence of life ; and that in this new direction scientific inquiry, though 

 at the outset pursued at the cost of some temporary suffering, would 

 in the end prove a thousand times more beneficent than it had ever 

 hitherto been. I said this because I saw that the very researches 

 which the lady deprecated were leading us to such a knowledge of 

 epidemic diseases as will enable us finally to sweep these scourges of 

 the human race from the face of this fair earth. 



This is a point of such special importance that I should like to 

 bring it home to your intelligence by a single trustworthy illustra- 

 tion. In 1850, two distinguished French observers, MM. Davainne 

 and Rayer, noticed, in the blood of animals which had died of the 

 virulent disease called splenic fever, small microscopic organisms 

 resembling transparent rods, but neither of them at that time at- 

 tached any significance to the observation. In 1861 Pasteur pub- 

 lished a memoir on the fermentation of butyric acid, wherein he de- 

 scribed the organism which provoked it; and, after reading this 

 memoir, it occurred to Davainne that splenic fever might be a case 

 of fermentation set up within the animal body by the organisms 

 which had been observed by him and Rayer. This idea has been 

 placed beyond all doubt by subsequent research. 



Some years in advance of the labors undertaken by Davainne, ob- 

 servations of the highest importance had been made on splenic fever 

 by Pollender and Brauell. Two years ago, Dr. Burdon-Sanderson 

 gave us a very clear account of what was known up to that time of 

 this disorder. With regard to the permanence of the contagium, it 

 had been proved to hang for years about localities where it had once 

 prevailed ; and this seemed to show that the rod-like organisms could 

 not constitute the contagium, because their infective power was found 

 to vanish in a few weeks. But other facts established an intimate 

 connection between the organisms and the disease, so that a review 

 of all the facts caused Dr. Sanderson to conclude that the contagium 

 existed in two distinct forms : the one " fugitive," and visible as 

 transparent rods; the other permanent but "latent," and not yet 

 brought within the grasp of the microscope. 



At the time that Dr. Sanderson was writing this report, a young 

 German physician, named Koch, occupied with the duties of his pro- 

 fession in an obscure country district, was already at work, applying, 



