330 SUMMARY OF CURRENT RESEARCHES RELATING TO 



If the animals are to be sectioned the author uses Lang's fluid boiling, or 

 the before- mentioned mixture of Lang's fluid and osmic acid. After 5 minutes 

 the fixative is removed, the object washed with water and treated with alcohol. 

 In two days the staining may be done. Imbedding is made in a mixture of 

 ordinary parafiin, tallow, and hard paraffin (about 1/10 of the mass). The 

 latter imparts a consistence suitable for riband sections. 



Preparing Diatoms in Cementstein.* — Mr. H. Morland recommends 

 the following plan for preparing and isolating the diatoms in Jutland 

 " cementstein " : — 



Slices about 1/25 in. in diameter are first of all prepared with 

 " Wellington knife-powder." When the slice is finished on one side, it is 

 attached with balsam, prepared slide downwards, to the slip on which it is 

 finally mounted. The balsam for this purpose must be hard, and it is 

 necessary to avoid bubbles under the section. The slices are fixed with 

 balsam slightly hardened, and then hardened off gradually by placing the 

 slips in a very cool oven for a week or ten days ; the balsam is thus 

 hardened throughout without bubbles. The second side of the slice 

 can now be rubbed down in the same way as the first side with " Wellington 

 knife-powder " and water on glass. As the section approaches completion, 

 care and very light pressure must be employed, the grinding being con- 

 tinued until the section begins to break away at its edges. The slip with 

 section attached is now washed with clean w^ater, wiped, and dried off with 

 a very gentle heat, not sufficient to soften the balsam, A very small 

 quantity of balsam is now put on the section, the cover placed on, and 

 pressed down hard. The slide is now placed in a cool oven for a iew days. 

 A ring of Bell's cement will enable it to be examined under an oil- 

 immersion lens without fear of the oil attacking and softening the balsam. 



In order to isolate the diatom sections, after preparing one side of the 

 slice, it is attached to a piece of glass about 1^ in. by 1 in. instead of 

 the ordinary 3 in. by 1 in. It is then immersed, still attached to the 

 glass, in benzol. After about half an hour it can be brushed off with a 

 camel's-hair pencil on to a glass slij), and cleaned of all balsam by brushing 

 with the camel's-hair pencil dipped in benzol. The slide is then trans- 

 ferred to methylated spirit to get rid of the residue of benzol, and, after 

 a short time, to clean water in a watchglass. The water is poured off 

 and a few drops of hydrochloric acid added, which at once separates the 

 diatoms contained in the section. The watchglass is now filled up with 

 distilled or filtered rain-water, allowed to settle, the liquid drawn off closely 

 by means of a fine pipette, and filled up with water again ; the process 

 being repeated until the whole of the hydrochloric acid has been got rid of. 

 The diatoms in the watchglass are now boiled in sulphuric acid ; and after 

 washing away the acid, the clean diatom sections are ready for selecting 

 and mounting. Mr. Morland states that some of his sections prepared 

 in this way aie net more than 1/3000 in. thick. 



Preparing Tubercle Bacilli. f — Herr Biedert dilutes 1 tablespoonful of 

 sputum with 2 of water and 15 drops liquor sodee, and then boils to fluidity ; 

 4 spoonfuls of water are again added, and the fluid reboiled until it is of 

 uniform density. If on cooling it docs not run well, more water is added ; 

 the fluid is kept bottled for two daj^s, and then the supernatant liquid 

 poured off so as to leave a quantity 5-8 mm. high in the flask. To this 

 some fresh egg-albumen is added, and after having been well shaken together 

 the fluid is used for cover-glass preparations. 



This method was found to give considerable increase to the number of 



♦ Journ. Quek. Micr. Club, ii. (1886) pp. 299-301. 

 t liei liner Klin. Wocbenschrift, 1886, Nos. 42-3. 



