260 THE AMEKICAN MONTHLY [November, 



should remain for two minutes. In order that the sections should be 

 perfectly cleared they are transferred from the turpentine to xylol, from 

 which they are mounted in balsam. It is recommended that the sec- 

 tions should pass successively through two xylol baths in order to 

 secure absolute elimination of the aniline oil. The xylol may be used 

 for a considerable number of sections. 



Dr. Kuhne employs a glass rod for transferring the sections from one 

 solution to another instead of the ordinary spatula or section lifter. 

 The end of a small glass rod is immersed in the fluid containing the 

 section, which is allowed to fold itself over the rod, and in this position 

 it is lifted from the fluid. The end of the rod is then gently immersed 

 in the second liquid, where the section unfolds itself from the rod and 

 floats upon the surface. In this way the danger of tearing them is 

 diminished and the time required for their transfer from solution to 

 solution is much shortened. This is an important consideration where 

 a large number of sections are to be stained. 



(/) Carbol-methylene-blue. — This is prepared by grinding in a 

 mortar 1.5 grams of methylene-blue with 10 c.c. of absolute alcohol 

 until disolved ; 100 c.c. of 5% carbolic acid is gradually added 

 and thoroughly mixed with the alcoholic solution. The resulting 

 liquid is preserved in a well-stoppered bottle until used. When 

 only a small quantity is to be employed it is better to prepare 

 only a half, or a quarter even, of the above quantity, as its staining 

 power is diminished by long standing. It should always be filtered 

 before using. 



(2) Weak acidulated water. — To 500 c.c. of distilled water add 

 10 drops of nitric acid. 



(j) Lithium water. — To 10 c.c. of distilled water add from 6 to 

 8 drops of a saturated watery solution of carbonate of lithium. The 

 saturated solution may be used as a decolorizing agent in sections with 

 over-stained nuclei. 



(4) Methylene-blue aniline oil. — About one-half gram of methy- 

 lene-blue is ground in a mortar with 10 c.c. of pure aniline oil. When 

 the oil is saturated with the coloring matter the entire mass is poured 

 unfiltered into a vial, where the undissolved coloring matter will settle, 

 leaving the saturated supernatant oil clear. To a watch-glass of pure 

 aniline oil add a few drops of the saturated methylene-blue oil until 

 the degree of colorization desired is obtained. 



Kiihne's Modification of the Koch-Ehrlich Method of Stain- 

 ing Tubercle Bacilli.* — The sections of tissue containing the bacilli 

 are stained for ten minutes in carbol-fuchsin (5) decolorized in a 30% 

 solution of nitric acid and then washed in 60% alcohol until they have 

 a rose color. From the alcohol they are transferred to a glass contain- 

 ing a considerable quantity of water to remove any of the acid that 

 might have remained in the section. The sections are now dehydrated 

 in absolute alcohol for three minutes, then placed in a solution of 

 methyl-green aniline oil (6), diluted one-half with pure aniline oil, 

 and allowed to remain in it for from five to ten minutes. From this 

 they are placed for two minutes in some essential oil, from which they 



* Ibid., p. 30. 



