ON THE BACTERIA. 157 



washed with distilled water. The cells, nuclei, fibres, and granules 

 now appear of a brownish colour, while the tubercle Bacilli stand 

 out in a beautiful blue tint. All other Bacteria and Micrococci 

 known to Koch, except those of tubercle and leprosy, lose their 

 blue by this process. 



More recently Koch's assistant, Dr. Erlich, has introduced a 

 new process. He first stains the tuberculous matter with magenta, 

 and then applies dilute nitric acid, which removes the colour from 

 everything but the Bacilli: and Dr. Heneage Gibbs has still further 

 improved upon this plan, by first staining with magenta, then 

 removing the colour from the surrounding matter by dilute nitric 

 acid, and afterwards adding a solution of Chrysoidin, which stains 

 the groundwork brown, leaving the Bacilli a reddish violet. 



Very recently a method has been suggested for the detection 

 of the Bacilli^ in the breath of consumptive patients. A respirator 

 is provided containing two layers of gun-cotton, and the patient is 

 ordered to breathe frequently during the day through this. The 

 external layer will intercept the suspended particles in the in-going 

 air, while the internal layer retains only the particles coming from 

 the lungs ; after being used for some time the internal layer is 

 dissolved in a mixture of rectified spirit and ether, and the solution 

 thus obtained is spread in the thinnest possible layer on a glass 

 sHde. It is then stained by one of the processes before mentioned, 

 when the Bacilli^ if present, are rendered visible. And still more 

 recently, by a similar process, the Bacilli have been detected in 

 the air of the Consumptive Hospital at Victoria Park. 



To cultivate the Bacilli^ pure serum of the blood of sheep or 

 cattle is steriHsed by keeping it for six days in test-tubes, plugged 

 with cotton-wool, and exposed daily for one hour, to a temperature 

 of 136^ F. After this it is heated for several hours at a temperature 

 of 150^ F., by which it is changed into a solid transparent mass. 

 It is then inoculated with any tuberculous matter, and kept at a 

 temperature of about 100° F., for one week, when it becomes 

 gradually covered with colonies of tubercle Bacilli. These Bacilli 

 are very small rods, in length about one-third that of a blood 

 corpuscle, in breadth about one-sixth of their length. From a 

 minute portion of this culture other inoculations are formed, 

 often for many generations, and the Bacilli thus produced are 



