ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 883 



is filled up with imbedding mass (1 part oil, 2 parts wax). When 

 quite cooled down the upper tube is removed. Cutting is best done 

 under water. 



The advantages claimed for this method, which is especially recom- 

 mended for preparations of the nervous system, are (1) the object is 

 not subjected to any pressure ; (2) the knife keeps sharp for a long 

 time. 



Imbedding Pharmaceutical Preparations.* — Dr. E. Vinassa im- 

 beds pharmaceutical preparations in a mixture of glycerin and gelatin 

 under the vacuum pump. This pump is of copper of 5 litres capacity, 

 heated by steam and connected with a Korting's pump. The floor of 

 the vacuum pump is covered with a layer an inch thick of paraffin 

 (melting point 56 ) ; during the whole time it is in use it is kept at a 

 temperature of 58°-60 C. In the bath are placed five tall and 

 widish boxes, which are for imbedding masses of different consisten- 

 cies. The formula for the imbedding mass is, Gelatina alba, 15 grm. ; 

 aqua ; glycerinum, aa, 100 grm. After the bath has been warmed 

 for some time the pressure is regulated so as not to exceed 200 mm. 

 The air in the cell-spaces is thus slowly driven out and the mass 

 begins to froth. After the lapse of some hours the air is so far 

 removed from the object that the stopcock of the air-pump may be 

 gradually opened until the manometer indicates about 720 mm. By 

 this measure the water is driven off, and in a few hours the gelatin 

 assumes the consistency of a stiff jelly. 



For hygroscopic or very mucilaginous roots, or such as have large 

 air-passages, the quantity of water in the imbedding mass must be 

 reduced one-half. Very fibrous tissues require to be left longer than 

 usual in the air-pump. 



Very dense woods such as Lignum juniperi and Taxi require to be 

 left in vacuo for four hours in a mixture of equal parts water and 

 glycerin, so that all the air is replaced by glycerin. This done tliey 

 are removed to a warm vacuum for eight to fourteen days until 

 frothing no longer occurs. "When this has been repeated two or three 

 times, they Avill be found quite ready for cutting. Woods rich in 

 resin or pigment must be first macerated in alcohol. The Rhizoma 

 Cartels, Amicse, Graminis, Stipitcs Dulcamarse, &c, after having been 

 saturated with gelatin, must be fixed in elder pith for cutting. 



The author has tried paraffin and its mixtures, and also oils mixed 

 with tallow or wax, but has always failed to obtain satisfactory 

 results. 



Imbedding Media for Diatonis.j — Mr. J. Deby uses, as imbedding 

 media for diatoms, chloride of zinc or chloride of magnesia mixed 

 with their respective oxides. As soon as the mixtures have become 

 hard, thin sections can be made in the same way as with ordinary 

 rock. If sufficient care is taken, it is not difficult to obtain sections 

 of a less diameter than the areola of a Triceratitnn or of a 

 Coscinodiscus. 



* Zeitschr. f. WIss. Mikr., ii. (1885) pp. H20-5. 

 t Journ. Quek. Micr. Club, ii. (188ti) pp. 308-9 



3 m 2 



