The Microscope. 313 



Robert Koch — His Work and Methods. — ^The entire second 

 story of the Board of Health building, (Berlin), is devoted to the 

 laboratory piu'poses, and, for convenience, has been divided into two 

 large working rooms, l^esides several other smaller apartments for 

 individual research. A single room, perhaps twelve feet square, with 

 double walls, between which is kept flowing a constant stream of 

 con'osive sublimate solution (1 to 1,000), is called the Cholera- 

 Zimmer, and in it is placed the little jar of cholera dejecta, which is 

 replenished from time to time from cholera infected localities. This 

 room is closely watched, and, except at stated intervals, no one is 

 allowed admission. Another room is fitted up with the apparatus 

 adapted to bacteriological study, such as steam and hot-air sterilizers, 

 and the various materials used in the preparation of the cultivating 

 media. The laboratory is heated by steam, and an even temperature 

 maintained day and night. The course which the writer was priv- 

 ileged to take began on the 15th of December, and closed on the 

 evening of the 24th. The daily session lasted from six in the morn- 

 ing until dusk. On entering, we were assigned to private rooms, 

 and each given a suit of stiffly -stai'ched linen clothes, which we con- 

 tinued to wear during the working sessions of the entire course. 

 Leaving all else behind, we proceeded to the so-called cooking room, 

 where we found the various ingredients necessary for the preparation 

 of the cultivating media already weighed out for us. These we com- 

 bined and sterilized, according to a set of rules peculiar to Koch's 

 system, and with which, I presume, most of my readers are now 

 more or less conversant. It requires the better part of two days to 

 make the nourishing substances; but these rather dry details over, 

 the work is more interesting. On the morning of the third day, we 

 made our first visit to the Cholera- Zimmer. In the centre of the 

 room, on a plate of glass, stood the little tin box, about the size of a 

 small pill-box, containing the cholera discharges from which we wei'e 

 to make the inoculations. The glass plate was covered with filter - 

 paper and saturated with sublimate solution. After inoculating the 

 tubes of food gelatin, they were poured out in the liquid state upon 

 sterilized glass plates, to allow the different species to colonize. By 

 this means, we were able to obtain a pure culture in about thirty-six 

 hours. To impress the peculiar growth of this organism more 

 strongly upon the mind, various other bacteria were cultivated at the 

 same time, and the contrast between them made apparent by their 

 manner of growth, rather than by their untrustworthy microscopic 

 appearances. In recalling the pleasant hours spent in this labora- 



