1882.J 



MICROSCOPICAL JOURNAL. 



127 



illumination; second, in the applica- 

 tion of a new method of bacterial 

 cultivation, viz., with a solid, transpa- 

 rent matrix of nutrition. 



On the 24th of March, 1882, Dr. 

 Koch laid before the Physiological 

 Society of Berlin, the result of his in- 

 cessant labor and study. His method 

 was substantially the following: — 



He took tuberculous matter in 

 the liquid state, spread it in a thin 

 coating on the cover-glass, dried it, 

 then heated it carefully so as to ren- 

 der it insoluble. He placed this in 

 an alcoholic solution of methyl, which 

 was prepared by dissolving one c. c. 

 of concentrated alcoholic solution of 

 methyl-blue in 200 c. c. of distilled 

 water, to which 0.2 c. c. of a 10 per 

 cent, solution of caustic soda had 

 been added. After 24 hours soaking 

 of the tuberculous matter in this so- 

 lution, or less if the solution is kept 

 at 104" F., the specimen was colored 

 blue by the methyl. It was then 

 well-washed with a very dilute solu- 

 tion of vesuvin. The vesuvin has 

 the peculiarity of neutralizing the 

 blue coloring of methyl in all the tis- 

 sues, turning them brown, but leav- 

 ing the bacilli unchanged. 



The specimen is now to be treated 

 with absolute alcohol, then put up in 

 oil of cinnantron, and finally prepared 

 with Canada balsam. As seen under 

 the microscope by Koch, using Abbe's 

 condenser without diaphragm and 

 the strongest Zeiss oil-immersion 

 lens, the tuberculous bacilli appear 

 distinctly differentiated as blue, rod- 

 shaped bodies, one-fourth of the 

 length of a red blood-corpuscle, /. e. 

 being about Troinr '^^ ^"^ vcvch. long, their 

 width \ of this, slightly cleft at one of 

 their ends. They resemble Bacillus 

 lepne, which also resists the staining of 

 vesuvin, but are thinner, and are not 

 split at one end. All the other bacilli 

 that Koch experimented upon, stain- 

 ing them blue with methyl, were 

 washed out by vesuvin. We possess, 

 therefore, in vesuvin, a chemical re- 

 agent as it were, for the tubercular 

 bacilli. Now, to establish the fact 



that these bacilli are the essential 

 cause of the disease and not post hoc 

 accident, Koch endeavored to isolate 

 these bacilli, and to inoculate with 

 them healthy animals. 



He employed a method that origi- 

 nated with Tyndall, employing a so- 

 called sterilized fluid; a special cul- 

 tivating substance was prepared out 

 of the serum of ox-blood, which he 

 first heated several times up to 48° C. 

 in order to destroy all organisms; 

 then he heated it again to 75" C. until 

 it was reduced to the consistency of 

 a brownish-yellow, transparent jelly. 

 This condition of the substance en- 

 ables usto recognize the slightest tur- 

 bidity that begins to form therein. In 

 this matrix, prepared in a test-tube, 

 was introduced a small particle of tu- 

 berculous matter from a freshly killed 

 and infected animal, which became 

 diseased by artificial inoculation. 



Within ten days the bacilli gave 

 off several spores, which developed 

 into rod-bacilli similar to those 

 brought out by the double-staining 

 described above. With those seeds a 

 new matrix was fertilized, and this 

 process was kept up by Dr. Koch for 

 200 days, always producing the same 

 bacilli. 



Those animals inoculated with the 

 early or later generations, with the 

 pure, grayish-white specks which ap- 

 pear as the propergerms in the matrix, 

 became rapidly diseased and died — 

 more rapidly than those inoculated 

 with the tuberculous matter of the 

 animal; even those animals that pos- 

 sess a comparatively greater immu- 

 nity from tuberculosis became dis- 

 eased to an extent involving all 

 their organs, when inoculated with 

 those cultivated bacilli. They were 

 injected by slight wounds in the veins, 

 eye and abdomen. The develop- 

 ment, however, goes on very slowly, 

 but it has its definite periods and its 

 limitation. The culture-fluid injected 

 without the bacilli never produced 

 tubercles. 



Koch found that they grow only at 

 a temperature between 30" and 41" C. 



