1889.] MICROSCOPICAL JOURNAL. 61 



The Philosophy of Mounting Objects.* 



By FRANK L. JAMES, M. D. 



In order that the student may understand the rationale of the pro- 

 cesses through which an object must be carried in its transition from 

 crude material to the finished slide, we will briefly describe the making 

 of a supposititious mount. Suppose the object to be a pathological speci- 

 men, a tumor for instance, recently removed. It is plain that the direct 

 examination of such an object can only be made with very low magni- 

 fying powers, such, for instance, as may be obtained by the use of a 

 pocket magnifier or Coddington lens. In order to reach the histolog- 

 ical elements we must use high powers, and these can only be used by 

 transmitted light — that is, light sent through the object to be examined. 

 We must therefore contrive a method by which the object, or a repre- 

 sentative portioiz of it, may be made translucent. This may be done 

 by taking a small portion of the material and mashing it out very thin 

 between two pieces of glass. In former times this method was fre- 

 quently resorted to, but as it could manifestly yield but very distorted 

 results it has long since been abandoned by those who use the micro- 

 scope as an instrument of precision. The other alternative at our dis- 

 posal is the cutting of a section from the object with a very keen knife ; 

 and here we meet with another difficulty, viz., the object is (usually) 

 too soft to offer such resistance to the passage of the blade as will en- 

 able us to cut a section of sufficient and uniform thinness. It is true 

 that formerly such sections were cut with a Valentine's knife and which 

 were supposed to be thin enough to yield practical results, but the de- 

 vice is now very rarely resorted to. The object must therefore be sub- 

 mitted to a process which will harden it and at the same time preserve 

 it. If we are in a great hurry to arrive at results we may attain the de- 

 sired end by freezing our object, but we will suppose that in the pres- 

 ent instance resort is had to one of the hardening and preserving fluids. 

 Having hardened the material our next step is to cut it into thin sec- 

 tions. Formerly this was accomplished by holding the hardened ob- 

 ject in the hand and slicing off a section with a razor. This process is 

 no longer used in exact and scientific work. Free-hand cutting has 

 given place to the microtome or section cutter — just as in exact work free- 

 hand drawing has yielded to photography. The object is therefore 

 transferred to a section cutter to be sliced into sections, and as these 

 sections must be made extremely thin and uniform, it must be securely 

 held in the microtome. It must be arranged so that it can be fed to 

 the knife and at the same time have no lost lateral motion. This ne- 

 cessitates embedding it in some liquid material that will harden around 

 it and hold it firmly in place. This done, the section-knife is brought 

 into play and the object is sliced to the requisite degree of thinness. 

 Here we must digress a little in order to explain subsequent operations. 



If we take any very thin substance — say a piece of paper — and place 

 it under the microscope in a dry state, we will find on examination that 

 we get a very insufficient idea of its intimate structure. If we moisten 

 the object with water we find that many details of the structure are 

 brought out and shown us which were invisible under the former ex- 

 amination. If, instead of water, we use glycerine or Canada balsam, 



* From Elementary Microscopical Technology. 



