1889.] MICEOSCOPICAL JOURNAL. 213 



about 5 minutes when the sections will have a dark brown, almost black 

 color. The sections are now transferred to a third watch-glass contain- 

 ing absolute alcohol, which will dissolve out the coloring matter from 

 the tissues of the section. The time required for the discolorization 

 varies from a few minutes to several hours, according to the thickness 

 of the section and the intensity of the stain. The time may be shortened 

 by transferring the sections to fresh alcohol when that in which it is 

 becomes highly colored. When the sections become colorless, or very 

 nearly so, they are to be cleared in turpentine, cedar oil, or xylol, and 

 mounted in balsam. 



A very satisfactory double stain may be obtained by staining the sec- 

 tions in an aqueous solution of Bismarck brown after they have been 

 decolorized in the alcohol. In this case it is better to transfer them 

 from the absolute to 95 per cent, and then to 70 per cent, alcohol before 

 transferring them to the staining solution. After the sections are 

 stained in this solution they should be washed in weak alcohol, dehy- 

 drated in stronger spirits, and finally cleared and mounted as in the 

 first case. By this method the bacteria will remain a dark blue, almost 

 black color, while the surrounding tissue will be stained a yellowish- 

 brown color. B} T this method one is able to determine whether the 

 micro-organisms are within or without the cell nuclei ; in fact, to de- 

 termine their location within the tissue. 



There ai"e many bacteria that will not retain the blue stain when 

 treated by this method. This fact renders the method of value in dif- 

 ferentiating between certain micro-organisms. 



Cover-glass preparations can be treated in the same manner as sec- 

 tions with equally as good results. 



EDITORIAL. 



Exchanges. — We have no idea of letting people use our columns 

 for advertising, for subscribers' notices, nor for any other purpose, unless 

 they deal squarely by their correspondents. Once in a great while 

 some one says he has had correspondence about exchanges, has done 

 his part and has failed to receive the slides agreed upon. Whenever 

 any subscriber feels that he is being maltreated in this way, let him 

 first state his grievance in a registered letter to the offending party. If 

 that person receipts for the letter and fails to give satisfaction, then refer 

 the correspondence and all facts to us. When the person offering to 

 exchange is proven to us to be using our columns in order to get and 

 not give slides, etc., we shall show him up to the world just as any 

 other microscopic object needs to be treated, and make him pay dearly 

 for his slides obtained under false representations. To simply drop 

 his advertisement or notice is too tame. The microscopist is bound to 

 use the scalpel, sunlight, and Abbe condenser on extremely minute 

 specimens. Verbum sap. 



o 



Corrections. — Some rather annoying errors crept into the August 

 number. On the cover, in the contents, correct folicle to follicle. On 

 page 180 and page 187 correct lense to lens. On page 1S1 correct title 

 of Prof. Tuckerman's article to Erethizon dorsatus, the common por- 

 cupine. On the same page circumvallate is mispelled twice. On page 

 190 change Melacerta to Melicerta. 



