STAINING BACTERIA. 245 



finally into clean oil of cloves, where they must remain 

 ten or fifteen minutes before mounting in balsam and 

 benzole. Preparations stained blue may be left in oil 

 of cloves for a week or more without doing them any 

 injury. 



The staining process has greatly facilitated the study 

 of the minuter forms of life. For staining Bacilli employ 

 the aniline reds as follows : Fuchsia in crystals, one 

 centigram ; alcohol, from twenty to twenty-five drops ; 

 distilled water, fifteen cubit centimetres : mix. The 

 colour stain taken by the bacilli is less intense than 

 that taken by the micrococci, and this serves to dis- 

 tinguish the one from the other. The minute size of 

 the bacilli renders their life history and study of their 

 growth under artificial cultivation a work of great 

 difficulty. Considerable importance, however, attaches 

 to these organisms obtained by cultivation, from the 

 fact that the resulting forms can be compared with 

 those found in connection with disease. Blood cor- 

 puscles are better studied under osmic acid staining 

 fluid, and which shows that most of the white corpuscle 

 may be divided into two or more kinds and forms. 

 One set is stained black by osmic acid, and another, 

 which contains granulous matter not fatty, is stained 

 red by an eosine solution. The best mode of showing 

 the three forms of corpuscles is to fix the blood in the 

 network of the smaller blood vessels ; for instance, in 

 the'choroid coat of the eye, by cutting the eye of the 

 frog into two parts, subjecting the section to the 

 vapour of osmic acid for twelve hours, then wash the 

 segment in distilled water, and detach the capillary 

 layer from the retina, spread it out on a glass slide and 

 stain it with ha3matoxylate of eosine. The corpuscles 

 will by this process be seen to be of three kinds the 

 ordinary, granular, and fatty. Care must be taken, as 

 the vapour of osmic acid is of a corrosive nature. 



M. Brandt finds hoematoxylin and Bismarck-brown 

 suitable colours for staining living unicellular organ- 

 isms. For amoebae and similar delicate bodies a 

 dilute solution of hcematoxylin must be allowed to act 

 for only a short time, not more than an hour, when 



