FERMENTATION. 267 



was found to vanish in a few weeks. But other facts 

 established an intimate connexion between the organ- 

 isms 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 re- 

 port, a young German physician, named Koch,' occupied 

 with the duties of his profession in an obscure country 

 district, was already at work, applying, during his spare 

 time, various original and ingenious devices to the 

 investigation of splenic fever. He studied the habits of 

 the rod-like organisms, and found the aqueous humour 

 of an ox's eye to be particularly suitable for their 

 nutrition. With a drop of the aqueous humour he 

 mixed the tiniest speck of a liquid containing the rods, 

 placed the drop under his microscope, warmed it suit- 

 ably, and observed the subsequent action. During the 

 first two hours hardly any change was noticeable ; but 

 at the end of this time the rods began to lengthen, 

 and the action was so rapid that at the end of three 

 or four hours they attained from ten to twenty times 

 their original length. At the end of a few additional 

 hours they had formed filaments in many cases a 

 hundred times the length of the original rods. The 

 same filament, in fact, was frequently observed to 

 stretch through several fields of the microscope. Some- 

 times they lay in straight lines parallel to each other, 

 in other cases they were bent, twisted, and coiled into 

 the most graceful figures ; while sometimes they formed 

 knots of such bewildering complexity that it was im- 



' This, I believe, was the first reference to the researches of Koch 

 made in this country. 1879. 



