ZOOLOGY AND BOTANY, MICBOSCOPY, ETO. 081 



be cut. The block is then cut out, softened a few minutes in absolute 

 alcohol, dipped once more in the celloidiu solution, and put on a cork. 



The block when cut out is better softened in ether and at once trans- 

 ferred to the cork. This procedure is not only more simple but more 

 effective. The preparation on the cork is then exposed to the air until 

 quite stiff and then allowed to float in 84 per cent, spirit until required. 

 By this method sections of the whole or any part of the eye may be made. 

 Anilin colours are to be avoided as they stain the celloidin. Logwood 

 also stains it, but acetic acid (1/2-1 per cent, solution) withdraws it in 

 twenty-four hours, leaving the tissue still coloured. Eosin may be 

 used as a contrast stain. Cedar and origanum oils are the best for 

 clarifying. 



Imbedding in Vegetable Wax.* — Dr. P. Francotte who has recently 

 investigated the qualities of vegetable wax as an imbedding medium, finds, 

 that whatever its potentialities may be, it is inferior to paraffin. The 

 method he advises is as follows : — After the object is fixed, hardened, and 

 stained, or not, it is laid in 94' spirit, kept at a temperature of 48" C. in a 

 water-bath. The wax is then added gradually, and in small pieces, until 

 the consistence is that of soup. If the object be small, the heat is continued 

 until all the alcohol has evaporated. If the object be large, the alcoholic 

 mass and the object are poured into a bulb fitted with a straight cooler or 

 tube, about three feet long; as the spirit condenses, it falls back into the 

 bulb, and when the object is properly saturated it is removed to another 

 vessel and the spirit driven off. The object is then oriented in a metal or 

 cardboard box filled with warm wax. When cool, the mass may be cut 

 with a microtome or by hand. The sections are fixed to the slide with 

 albumen or gum. The slide is then heated in a water-bath to 50' C, and 

 alcohol added until the wax is dissolved. If not coloured en masse, the 

 sections may now be stained and then dehydrated, and afterwards cleared 

 up in cloves, cedar, or bergamot oil, or they may be mounted in 

 glycerin. 



The advantages this medium has over paraffin are, that it dispenses with 

 such fluids as toluol, xylol, benzine, and chloroform, and hence is suitable 

 for animal tissue where these fluids are contra-indicated. It is available 

 also for the examination of micro-organisms in tissues ; in this it is superior 

 to paraffin, for it is always difficult and frequently impossible to discover 

 microbes in tissues impregnated with paraffin. Its most important dis- 

 advantages are, that it is difficult to obtain sections thinner than * 01 mm., 

 and to make out when the object is properly saturated. 



Baskets for the suspension of objects in paraflin.t — Mr. H. Garman 

 recommends the use of wire baskets for suspending objects in paraffin. 

 Such a basket is easily made by coiling annealed wire as shown in fig. 191, 

 beginning at the centre of the bottom and working outwards to the margin, 

 then making the handle h, and finishing with a triangular base b. In 

 use it is placed in the melted paraffin, the triangular base supporting and 

 keeping it from the bottom of the paraffin basin, and it can be removed by 

 means of the projecting handle, which is made of such length that it does 

 not interfere with the glass cover of the basin. For very small objects a 

 hammered wire spoon, like that used by Dr. Mark, is mounted in the same 

 way as the basket (fig. 192). This method of suspending objects in paraffin 



* Bull. Soc. Beige Micr., xiii. (1887) pp. 140-4. 

 t Amer. Naturalist, xxi. (1887) pp. 596-7 (3 figs.). 

 1887. 2 Y 



