ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 331 



The section may be stained by Pappenlieim's pyron in-methyl-green 

 method or with Unna's polychrome methylen-blue. 



The authors modified the foregoing technique by using dextrin as 

 a medium for freezing the celloidin-l)lock and cutting the sections with 

 a freezing microtome. The procedure then was as follows. The plug of 

 cerebrospinal fluid was prepared as above and embedded in S p.c. 

 celloidin. When dry the block was immersed in dextrin, made up as 

 follows : dissolve 1 part of dextrin in 2 parts of boiling water, filter 

 through white cotton wool and add 1 p.c. of carbolic acid. The block is 

 left in the dextrin until the following day or until required : this pre- 

 vents the celloidin from becoming too hard. The block is then sectioned 

 on an ether-freezing microtome. The sections are placed in warm water 

 to remove the dextrin, and then mounted on slides. 



The celloidin is then dissolved out, first by methyl-alcohol, then Ijy 

 absolute alcohol, lastly by 75 p.c. alcohol, and stained with pyronin- 

 methyl-green. The sections should not l)e too thin, as the stain is 

 easily washed out, and the cell differentiation then becomes poor. 



New Method of Staining Diphtheria Bacilli.* — Marie Raskin 

 recommends the following stain. Glacial acetic acid 5 c.cm., distilled 

 water 95 c.cm., alcohol (!)5 p.c.) 100 c.cm., saturated solution methylen- 

 blue 4 c.cm. Ziehl's carbol-fuchsin solution 4 c.cm. 



Drop mixture in a thin layer over the smear or film on the cover- 

 glass : heat over flame. The alcohol ignites and is permitted to burn 

 off, after which the specimen is washed in water and dried. The entire 

 process takes 20-25 seconds. The polar bodies are stained blue and the 

 bacilli bright red. Even in smears with a preponderance of other 

 bacteria, individual diphtheria bacilli may be readily identified. 



6) Miscellaneous. 



Modified Centrifuge Fitting.f — For the investigation of certain 

 problems in cytological analysis, for studying the viscosity of cytoplasm 

 and the relative density of cytoplasmic inclusions, E. Faure-Fremiet 

 has applied to the centrifuge a modification which permits of the 

 centrifugalizing of a preparation mounted between slide and cover-slip. 

 In place of the moval)le ring, which carries the centrifuge tube-holder, 

 there is fitted to the apparatus a rectangular structure, capal)le of 

 holding a slide of the usual dimensions, and provided with solid stays 

 to prevent lateral movement. 



Dilution of Stock Solutions. if — E. Lowe gives a simple rule for 

 the preparation of dilute solutions of stains, and other reagents from a 

 stock solution. Into a measuring cylinder pour of the stock solution 

 a number of cubic centimetres corresponding to the percentage strength 

 of the required dilute solution, and then add of the diluent enough to 

 bring up the total bulk of fluid to a quantity coriesponding to the 

 percentage strength of the stock solution. For example : from a 1(:» p.c. 

 solution to prepare a 3 p.c. solution, put 3 c.cm. of the stock solution 

 into a measuring-glass, and make up with the diluent to 10 c.cm. 



* Trans. American Micr. Soc, xxxii. (1913) pp. 74-5. 



t C.R. Soc. Biol. Paris, Ixxiii. (1913) p. 616. 



X Zeitschr. wiss. Mikrosk., xxix. (1913) pp. 545-7. 



