Cutting Sections, &c. Bij Drs. Johnston- Lavis and Vosmaer. 201 



advantages over Koch's method, and is not much longer than the sec- 

 tionizing of pumice-stone devised by the first-named of the authors of 

 this paper.* In fact this process was suggested to us by this latter 

 method combined with that of Prof. 0. Sankey, which most beautifully 

 demonstrates how even a tissue like the brain, with its delicate cells and 

 nerve-filaments, can withstand drying. 



The method we now describe has the following points in its favour : — 

 it renders the protoplasm sufiiciently hard to be treated as fossil sponges ; 

 it does not destroy histological details more than a paraffin imbedding ; 

 it permits the making of sections of unlimited size ; every spicule or other 

 unfixed object remains in its place. The objections to it are its somewhat 

 tedious character, requiring patience and a certain amount of skill and 

 ingenuity in carrying out the various operations; but after all, this 

 equally applies to all methods. 



The materials required are, besides the specimens and staining mate- 

 rials, Canada balsam dissolved in benzole, a thick and a very thin solu- 

 tion, hard balsam such as is used in cutting rock sections, a grindstone 

 with a flat side,t and a good-sized hone, say 2^ x 1^ X 8 in., a solution 

 of soap in equal parts of alcohol and water, and a small stream of clean 

 water. 



A thin slice is cut with a very sharp thin knife from the whole or 

 part of a sponge hardened in absolute alcohol of a thickness of from two 

 to five lines, according to the size and structure of the specimen. This, 

 after the usual staining process, is returned to absolute alcohol and a few 

 drops of benzole are added ; after an hour some more benzole, and so on. 

 The next day the object may be placed in pure benzole. If one adds the 

 benzole too quickly the object shrinks and is spoiled. 



From the benzole it is transferred either into the benzole-balsam 

 solution or lumps of balsam are added to the benzole bath in which it 

 was. The quantity of the balsam is either increased by the use of a 

 more concentrated solution or by adding more hard. 



After the object is well penetrated it may be dried in the air for one 

 day, after which it is transferred to a kind of hot-air bath, of which we 

 give a sketch and description. Provided the tissues are thoroughly 

 penetrated by the balsam, they can withstand complete drying up, and 

 even in order to accelerate the process, they can be exposed to a tempe- 

 rature of 80° C. or more. Usually after some days, or in the case of 

 large objects after some weeks, the section is hard enough for grinding. 

 In order to be successful it is necessary to see that balsam fills every 

 hole, and if such is not the case, to apply some thick solution which 

 may be used warmed. If, on commencing to grind, as it will sometimes 

 occur, that the balsam is not hard everywhere, or even if one can make 

 an impression with the nail, it must be returned to the oven. To pre- 

 vent fracturing in consequence of the balsam being unannealed, it is 

 advisable to gradually lower the temperature toward the end of drying. 

 In cases of very large slices it is convenient to bring them in complete 

 contact with the surface of the glass slips upon which the specimens are 



* See this Journal, 1886, p. 22. 



t An ordinary grindstone trimmed with an old file, or a piece of flat sandstone 

 answers very well. 



1887. P 



