832 SUMMARY OF CURRENT RESEARCHES RELATING TO 



;8. Technique.* 

 (1) Collecting Objects, including' Culture Processes. 



Solid Medium for the Culture of Micro-organisms.f — Dr. Schenk 

 recommends the outer layers of the white of the eggs of marsh fowl and 

 waders as a suitable medium for breeding micro-organisms, on account of 

 its great transparency when coagulated at temperatures of 65°-70° C. This 

 albumen can be diluted with a fourth of its volume of water before coagu- 

 lation, and can be mixed with salt, dextrin flour, sugar, glycerin, &c. Of 

 course discontinuous sterilization must be employed as usual. 



New kind of solid Blood-serum— Blood-serum Plates.^ — Dr. P. G. Unna 

 states that by the addition of peroxide of hydrogen and carbonate of soda 

 to blood-serum he produces a fluid which coagulates at a high temperature, 

 can be easily sterilized, and preserves its transparency and suitability as a 

 nutritive medium for micro-organisms. 



The procedure is as follows : — To a small quantity of calf's blood-serum 

 hydrogen peroxide is added drop by drop, and the mass kept agitated until the 

 brownish-yellow mixture clears up and assumes quite a white colour. The 

 quantity of peroxide of hydrogen added is equal to about half the volume 

 of the serum, and as the commercial fluid is acid, a 2 per cent, solution of 

 sodium carbonate must be added until a slight alkalinity is perceived. It 

 is then filtered until quite clear. The serum is then solidified in Koch's 

 apparatus at a temperature of 90°-120°, according as less or more peroxide 

 and carbonate have been added. The condensation water having been 

 poured off", discontinuous sterilization is continued until sufficient. 



For serum plates the author adds 10 per cent, gelatin or 6 per cent, 

 agar-agar to the mixture if the blood-serum have lost its susceptibility to 

 coagulate owing to an excessive addition of alkali. 



Preserving cultivations made by Koch's plate method.§ — Dr. C. Garre 

 removes a piece of gelatin 2-5 sq. cm. in size, and in which is the colony to 

 be transplanted to a slide, with a thin moistened knife. Should the gelatin 

 layer roll up, it is to be immersed in water, and then the piece is dried 

 under a bell-jar or in a sulphuric acid apparatus until it is reduced to one- 

 half or one-third its original volume. A drop of glycerin-gelatin fluidified 

 at a gentle heat is then added in order to prevent the gelatin tablet from 

 crumpling up. The cover-glass is next imposed. 



This manipulation must be carefully carried out, otherwise the colonies, 

 especially if luxuriant, might be damaged. As the drying stops develop- 

 ment the organisms may be fixed in any stage of their existence ; the colonies 

 do not undergo any change with keeping, and, if desired, by merely 

 removing the cover, they are always available for cover preparations or 

 pure cultivation. 



Modification of Koch's plate method for the isolation and quantitative 

 determination of Micro-organisms. |1 — Dr. E. Esmarch's modification simply 

 consists in the use of a test-tube, the interior of which is covered with a layer 

 of some nutritive medium, e. g, gelatin. The test-tube, the mouth being 

 covered with a rubber cap, is laid horizontally on a vessel filled with ice- 

 cold water, and turned round with the hands until the gelatin has set. 



* This subdivision contains (1) Collecting Objects, including Culture Processes; 

 (2) Preparing Objects ; (3) Cutting, including Imbedding and Microtomes; (4) Staining 

 and Injecting; (.5) Mounting, including slides, preservative fluids, &c. ; (6) Miscella- 

 neous. 



t Allgemein. Wiener Med. Ztg., xxxii. (1887) p. 214. 



X Monatshefte f. pract. Dermatologie, v. (1886) No, 9. 



§ Fortschr. d. Med., iv. (1886) p. 392. || Zeitschr. f. Hygiene, i. (1886) p. 293. 



