CHAPTER I. 7 



centimetres high and 27 millimetres internal diameter. Each of these 

 will then take two slides, English size, placed back to back. 



7. Resume of the General Method. To sum up, you may either 

 fix, wash out, stain, wash, dehydrate, clear, imbed, cut sections, clear 

 and mount them in balsam ; or fix, wash, dehydrate, clear, imbed, 

 cut, stain, wash, dehydrate, clear, and mount according to choice. 



8. Preparation of Entire Objects, or of Material that is not to be 

 sectioned. The treatment of objects which, can be studied without 

 being cut into sections is identical with that above described, with 

 the omission of those passages that relate to imbedding processes. 

 Its normal course may be described as fixation, washing out, staining, 

 treatment with successive alcohols of gradually increasing strength, 

 final dehydration with absolute alcohol, clearing, and mounting in 

 balsam. 



In the preparation of entire objects or structures that are intact and 

 covered by an integument not easily permeable by liquids, special care 

 must be taken to avoid swelling from endosmosis on the passage of 

 the objects from any of the liquids employed to a liquid of less 

 density, or shrinkage from exosmosis on the passage to a liquid of 

 greater density. This applies most specially to the passage from 

 the last alcohol into the clearing medium. A slit should be made in 

 the integument, if possible, so that the two fluids may mingle without 

 hindrance. And in all cases the passage is made gradual by placing 

 the clearing medium under the alcohol, as described ( 5). Fluids 

 of high diffusibility should be employed as far as possible in all the 

 processes. Fixing agents of great penetrating power (such as picric 

 acid or alcoholic sublimate solution) should be employed where the 

 objects present a not easily permeable integument. Washing out 

 is done with successive alcohols, water being used only in the case 

 of fixation by osmic acid, or the chromic mixtures or other fixing 

 solutions that render washing by water imperative. Staining is 

 done by preference with alcoholic staining media. The stains most 

 to be recommended are Grenacher's borax-carmine, or one of Mayer's 

 alcoholic carminic acid or hsematein stains. Aqueous stains are 

 more rarely indicated, though there are many cases in which they 

 are admissible, and some in which they are preferable. 



9. Minute Dissections. These are best done, if necessary, in a 

 drop of clearing agent. I recommend cedar- wood oil for this purpose 

 as it gives to the tissues a consistency very favourable for dissection, 

 whilst its viscosity serves to lend support to delicate structures. 

 Clove oil has a tendency to make tissues that have lain in it for r.ome 



