ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 817 



should further describe the precautions required to prevent con- 

 tamination and the neglect of which may entirely nullify the value of 

 the cultivation." 



Another form used by M. Miquel is shown in fig. 136. By the 

 tube A air is projected on the drop of nutritive liquid at the under 

 side of the plate L L, and this 



having been done, the tube is Pjq_ 13g_ 



■withdrawn, and the hole closed 

 with a piece of cork ; the tube 

 B, which contains some wad- 

 ding, serves as the aspirator. 



Dr. Koch describes the 

 method adopted by Hesse for 



defining the exact quantity of air from which the spores originate. A 

 glass tube 12 in. by 2| in. is closed at each end with indiarubber 

 coverings, in one of which a glass pipe is inserted, while in the middle 

 of the other is an opening about 3/8 in. in diameter. Gelatine is 

 placed along the bottom of the tube, which is in a horizontal position. 

 The smaller pipe is then placed in connection with an exhausting 

 apparatus and a given quantity of air is forced through, the bacteria 

 and spores falling on the gelatine. 



Staining of Schizomycetes in Sections and Dry Preparations.* 



■ — C. Gram proposes the following method for producing an isolated 

 staining of pneumonia-cocci, leaving the nuclei and other elements of 

 the tissue uncoloured, the deep staining of the cocci usually found in 

 the sweat-cells causing them to be much more readily found than in 

 ordinary preparations. The method he considers applicable also to 

 almost all examinations of Schizomycetes in sections and dry pre- 

 parations. 



He takes the ordinary Ehrlich's anilin-gentian-violet solution. 

 The sections to be examined for Schizomycetes must be preserved in 

 absolute alcohol and brought direct from it to the staining fluid ; 

 here they remain from 1-3 minutes (in the case of preparations of 

 tubercular bacilli from 12-24 hours) ; then placed in an aqueous 

 solution of potassium biniodide (1 part I, 2 parts KI, 300 parts 

 water), without or after a slight washing with alcohol, where they 

 remain again from 1-3 minutes. A precipitate takes place in the 

 iodine solution, and the sections, previously a dark blue-violet, 

 become a blackish purple-red. They are now laid in absolute 

 alcohol until the colour is again entirely removed, the alcohol being 

 renewed once or twice. They are then clarified in the ordinary way 

 by clove-oil, the remainder of the pigment being given ofi" to the oil. 

 The nuclei and the fundamental tissue are now coloured light yellow 

 by iodine, while the Schizomycetes, if present in the section, are of a 

 conspicuous intense blue colour, often nearly black, the colour being 

 much deeper than in any other mode of staining. After the applica- 

 tion of alcohol, tho sections may be placed for a moment in a weak 



* Fortschr. d. Medicin, ii. (1884) No. G. See Bot. Centralbl., xviii. (188i) 

 p. 383. 



