COLLODION AND OTHER IMBEDDING METHODS. 129 



even less, or better into chloroform, or vapour of chloroform, 

 for a few minutes, in order that the joint may harden 



Dr. LINDSAY JOHNSON informs me that he finds it very 

 convenient to take for this purpose the cement used by metal 

 turners for fastening metal objects on to boxAvood chucks. 

 The exact composition of this cement varies somewhat, but 

 an average one is beeswax, 1 part ; rosin, 2 parts. To use 

 it you must get the block of celloidiu perfectly dry at the 

 bottom, then warm the object-holder slightly, if possible 

 over a flame ; drop on to it a few drops of melted cement, 

 and press on to it the block of collodion, which will be firmly 

 fixed as soon as the cement is cool that is in a few seconds. 



For objects of any considerable size it is important not to 

 use cork for mounting on the microtome, especially if the 

 object-holder be a vice ; for cork bends under the pressure of 

 the holder, and the elastic collodion bends with it, deforming 

 the object. I have seen large embryos so deformed in this 

 way that the sections obtained were true calottes, segments 

 of a sphere. If the object -holder be of the cylinder type, 

 as in the later forms of the Thoma microtome, the above- 

 desci-ibed accidents will be less likely to happen, and a good 

 cork may be used ; but even then, I think, wood is safer. 

 GAGE has recommended bits of glass cylinders. JELINEK 

 (Zeit. f. wiss. Mik., xi, 2, 1894, p. 237) recommends a sort of 

 vulcanite known as " Stabilit," which is manufactured for 

 electrical insulation purposes. It is supplied in suitable 

 blocks by JUNG (presumably also obtainable through GRUBLER 



AND Co.). 



Sections (from such masses as have not been cleared 

 before cutting) are cut with a knife kept abundantly wetted 

 with alcohol (of 50 to 85 or even 95 per cent.). Some kind 

 of drip arrangement will be found very useful here. Apathy 

 recommends that the knife be smeared with yellow vaselin ; 

 it cuts better, is protected from the alcohol, and the mobility 

 of the alcohol on the blade is lessened. 



The knife is set in as oblique a position as possible. 



Very brittle sections may be collodionised as explained 

 above ( 136). 



The sections are either brought into alcohol (of 50 to 85 

 or 95 per cent.) as fast as they are made; or if it be desired 

 to mount them in series, they are treated according to one of 



~ 9 



