KEMARKS ON TECHNIQUE 15 



counter-stained with safranin or f uchsin, as is the case with the Pneumo- 

 bacillus. In cultures the capsules are not so frequent ; they may, 

 however, be still quite distinct e.g., in the case of Pneumobacilli ; in 

 a smear made from a culture they appear to fuse together, and form 

 a mass which separates the individual organisms from each other. 

 At over-heated spots clear spaces are shown. Capsules are often seen 

 in Pneumococci from the condensed water, and occasionally, too, from 

 the surface, of an agar or blood-serum tube (cf. p. 184, Fig. 32). 



In sections of hardened tissues e.g., cornea infected with Pneumo- 

 cocci the capsules are not clearly seen ; where large masses of the 

 organism occur, it is obvious, from the looseness of their packing 

 together, that some separating medium lies between the individuals. 



Staining of Cilia. 



1. Loffler's method gives good results. A surface agar culture, not more than 

 twenty-four hours old, is taken, and its motility proved in a hanging- drop. A 

 cover-glass is prepared by cleaning with ether and alcohol, and heating on an iron 

 plate, so that it is absolutely fat-free. The merest trace of the culture is rubbed 

 on the glass in a drop of water ; after drying, fix by carefully passing three times 

 through a flame. Too much heating damages the specimen. Mordant in the follow- 

 ing solution : Tannin, 2 ; aqua, 8 ; sat. sol. ferri sulph., 5 ; alcohol, 1. 



(a) Enough of this is run through a filter on to the cover-glass to entirely cover it. 

 The whole is then carefully warmed until steaming (greater heat damages), and 

 the mordant is allowed to act for one minute (longer is harmless). 



(6) Wash with water under a tap. 



(c) Rapidly wash in 96 per cent, alcohol. 



(d) Dry rapidly in a draught. 



(e) Stain with Ziehl's solution : Fuchsin, 1 ; abs. alcohol, 10 ; formol, 5 ; aq. 

 dist.,100. 



(Czaplewski recommends warm anilin-water-fuchsin solution, which, by the addi- 

 tion of caustic soda, is in a condition of suspension.) 



Enough of this Ziehl's solution is filtered on to the cover-glass, which is then 

 warmed till steaming ; the fluid is allowed to act for about five minutes. 



(/) Thoroughly wash, dry, and then mount in balsam. 



2. Van Ermengem's Method. Mordant for five minutes with warm osmium 

 mixture (60 c.cm. of a 26 per cent, solution of tannin, 30 c.cm. of a 2 per cent, osmic 

 acid, 4 to 5 drops of glacial acetic ac.). Wash first with water, then with alcohol, 

 Moisten for several seconds with 0'5 to 2 - 5 per cent. sol. of silver nit. ; then place for 

 several seconds, without washing, in a mixture of ac. tannic., 3 ; ac. gallic., 5 ; sod. 

 acet., 10 ; aq. dist., 350 ; and back again into the silver till the preparation begins 

 to blacken. Wash with water, dry, and mount. 



3. Luca ValentVs Method. Drop a few drops of 20 per cent. ac. tannic. on the 

 preparation ; wash, warm for a short time with Ziehl's solution ; wash ; dry ; and 

 mount. According to Lehmann and Neumann, this simple method gives reliable 

 results. 



I have often been able to confirm the general experience that motility 

 (in a hanging-drop) and the presence of cilia are very irregular, 



