ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 387 



lowish, translucent, but slightly opalescent mass of the consistence of 

 coagulated gelatine. Its translucency permitted the growth of 

 organisms, either on its surface or in its depth, to be readily recog- 

 nized by the resulting opacity. In order to increase the area of the 

 free surface of this culture soil, it is recommended to incline the test- 

 tube at the moment of coagulation. A small fragment of excised 

 tissue was introduced into a tube under special precautions, to avoid 

 contamination with ordinary bacteria of putrefaction. Fresh miliary 

 tubercle answers best, taJien from an animal affected with inoculation- 

 tubercle, and killed shortly before. If the glass is kept at a tempera- 

 ture of 37° or 38° C, at the end of about ten days the first effect of 

 culture is observable as fine white points and streaks on the surface of 

 the serum. Fresh glasses may be inoculated from this first culture, 

 and so a series of generations may be obtained. Some of these series 

 of cultures were continued for two hundred days. Under the micro- 

 scope these greyish- white masses on the surface of the serum are found 

 to consist of precisely the same bacilli as can be demonstrated by 

 means of the method of double coloration, in the primary tuberculous 

 tissue. If a small portion is inserted into the anterior chamber of the 

 eye of an animal, injected into its blood, or inoculated beneath its 

 skin, there results a wide-spread tuberculosis of almost all the organs 

 and tissues, which has a more rapid course than when the inoculation 

 is made with ordinary tuberculous material. The first symptoms are 

 to be observed in guinea-pigs ten days after the inoculation. Even 

 animals which enjoy an almost complete immunity from tuberculosis, 

 such as dogs and rats, are affected rapidly, and with certainty. In 

 some of the animals which died after these inoculations, the amount 

 of tubercle developed in the tissues was enormous, being hardly ever 

 equalled in the human subject. 



Koch determines the limits of temperature between which the 

 tubercle-bacillus can develope and multiply. The minimum temperature 

 he finds to be 80° C, and the maximum 41° C. He concludes that, 

 unlike the Bacillus anthracis of splenic fever, Avhich can flourish freely 

 outside the animal body, in the temperate zone animal warmth is 

 necessary for its propagation. He also points to the grave danger of 

 inhaling air in which particles of the dried sputa of consumptive 

 patients mingles with dust of other kinds. 



These experiments seem to demonstrate that the organism which 

 is revealed by the method of double coloration is really the patho- 

 genic element of tuberculosis. The researches appear to have been 

 conducted with admirable care. The experiment will no doubt be 

 soon repeated. Indeed, in the brief interval which has elapsed since 

 the demonstration by Koch, on March 24th, his observations have 

 received independent confirmation by Baumgarten, who has published 

 in the Centralblatt fiir Med. Wiss. an account of his observations. In 

 every new formation of artificially produced tuberculosis in the 

 guinea-pig he found innumerable quantities of the rod-shaped bacteria 

 infiltrating the area in diminishing intensity from the centre to the cir- 

 cumference. As far as the tubercular growth can be traced the 



