342 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(5) Mounting-, including Slides, Preservative Fluids, &c. 



Thymol in Microscopical Technique.* — Dr. G. Martiuotti concludes 

 from bis own experiments and the researches of others that although 

 thymol may have a useful application in microscoiiy as an antisej)tic, it 

 should not be employed when the tissues to be examined have been or are 

 to come in contact with chromic acid or its salts. 



If to a watery solution of chromic acid a watery solution of thymic acid 

 be added, a precipitate forms, even when not exposed to light, and this 

 precipitate is devoid of the characteristic smell of thymol. After washing 

 the precipitate, the filtrate is found to be a yellow odourless powder, which 

 examined microscopically consists of amorphous granules and a few small 

 prismatic crystals. This j^recipitate is insoluble in water, insoluble or 

 nearly so in alcohol, ether, chloroform, benzine, in water acidulated with 

 sulphuric, hydrochloric, nitric, acetic, formic, and oxalic acids, in ammonia, 

 in anilin diluted with alcohol. If an alcoholic solution of thymol be added 

 to the watery solution of chromic acid the action is so energetic that the 

 temperature rises from 70° to 80" C. The precipitate is produced as 

 before, but the mass assumes a blackish colour, as if mixed with some 

 carbonaceous matter. 



Again, if thymol crystals be thrown into the chromic acid solution they 

 become invested by a precipitate, while their central parts retain their usual 

 character. With solution of potassium bichromate similar results follow, 

 but more slowly. 



Hence a chemical action takes jjlace between thymol and chromic acid, 

 and this action is a process of oxidation. So the writer assumes from the 

 researches of Lallemaud, Carstanien, and others who have examined, the 

 relations and composition of thymol. 



As remarked above, the conclusion arrived at is that thymol is unsuit- 

 able as a microscopical reagent in conjunction with chromic acid or its 

 salts. With other reagents, such as picric acid, carmine, gum, and gelatin, 

 thymol works well. 



Hilgendorfs Apparatus for Dehydrating Microscopical Prepara- 

 tions.! — Herr F. Hilgendorfs apparatus consists of a test-tube (for small 

 objects, about 50 mm. long and 6 mm. broad) into which is filed, about 

 6-10 mm. above the bottom, a small hole. The aperture may, if necessary, 

 be lessened by means of a wood-splinter. The object is then placed in this 

 tube, partially filled with weak spirit, and the upper end closed with a cork. 

 Thus prepared, the tube is inserted into a closed vessel filled with absolute 

 alcohol. Through the small hole the latter finds its way into the tube, and 

 continues to do so for a half to one hour. At a height of 1 cm. diosmosis 

 was found to require several days, but the rapidity of the action can be 

 proportionately increased by filing the hole lower down. Several tubes, 

 and this is a great advantage, can be placed in the outer vessel at the same 

 time. It is recommended to use some hygroscopic substance, as burnt 

 copper sulphate, &c., to keep the dehydrating fluid as concentrated as 

 possible. 



Method for treating Serial Sections imbedded in paraffin by Weigert's 

 method. J — -Weigert's method of making serial sections of celloidin pre- 

 parations was described in this Journal, 1886, p. 349. 



Prof. H. Strasser describes the following improved method, in which 



* Zoitschr. f. Wiss. Mikr., iii. (1886) pp. 351-8. 



t SB. Gcsell. Naturf. Fieunde zn Berlin, 1886, pp. 133-6. 



X Zeitschr. f. Wiss. Mikr., iii. (1886) pp. 346-50. 



