258 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
cover-glass is next carefully raised, and a small piece of glycerin-jelly 
put in the water or glycerin which remains on the slide. The slide is 
then heated to melt the jelly. Air-bubbles having been pricked out, 
the cover-glass is replaced in its original position. It is advisable to 
take too little rather than too much glycerin-jelly, as the deficiency is 
easily made good afterwards. 
Venetian Turpentine as a Mounting Medium."^ — Dr. J. Vosseler 
recommends Venetian turpentine for mounting specimens permanently, 
on the ground that it possesses all the advantages of the ordinary resinous 
media employed for the purpose ; that in some resj)ects it is superior to 
them ; and that it is cheaper. 
Venetian turpentine is obtained from the larch, and is found to 
consist of a resin and an ethereal oil ; consequently it is to be classed 
among the balsams. In colour and consistence the raw material 
resembles honey, but is sometimes brownish from admixture with 
minute fragments of bark. 
To obtain a suitable solution the author merely mixes equal volumes 
of the crude balsam and 90 per cent, alcohol in a tall glass vessel, the 
top of which is protected from dust, and allows this to stand in a warm 
place for three or four weeks. The processes may be hastened by 
increasing the heat in an incubator. A clear yellowish or sometimes 
greenish mixture is obtained, and this is at once ready for use, as 
the impurities have already sunk to the bottom. These impurities may 
be extracted with greater rapidity by filtration. If the filtrate should 
bo of a brownish hue, it must be thickened anew until the yellow colour 
returns. If the balsam be applied in a too fluid form it may become 
milky : should this turbidity be not too great, it will be found to dis- 
appear in a day or two ; if considerable, the balsam must be dissolved 
out in 96 per cent, alcohol, and the specimen be remounted. The 
ordinary consistence of Canada balsam is that most suitable for the 
solution of Venice turpentine. 
Prepared in the foregoing manner, Venice turpentine mixes with the 
reagents constantly in use in histological technique — for example, ether, 
alcohol 100-96 per cent., chloroform, pure carbolic acid, creosote, xylol, 
benzol, toluol, and the ethereal oils. Preliminary clarification of 
sections or pieces of tissue is quite superfluous, although when an entire 
animal, e. g. a small arthropod, is to be mounted, it is preferable to pass 
it through turpentine or creosote first. Hence, with a few exceptions, 
specimens are to be transferred directly from 96 per cent, spirit to this 
medium. 
The finer details of structure are better shown in the medium than 
in dammar or balsam, but it is remarked that these details may disappear 
shortly after mounting, to reappear again on the second or third day. 
The medium behaves towards staining agents in the same way as other 
resinous substances, and is perfectly suited for sj^ecimens and sections 
imbedded in celloidin or paraffin. 
The only inconvenience connected with the medium indicated by 
the author is that it is as slow to dry as dammar ; but when dry it is 
harder and less brittle than balsam or dammar. 
* Zeitschr. f. Wiss. Mikr., vi. (1889) pp. 292-8. 
