1891.] MICKOSCOPICAL JOUKIMAL. 37 



A good razor of this make has the properties, so greatly to be desired 

 in a knife for this work, of taking and holding ?i very fine edge. It 

 may be attached to the knife-carrier by means of one of the holders sold 

 for that purpose. It should be of the form known as " half hollow 

 ground," the full hollow ground being too thin back of the edge. 

 The form of a section knife and the way in which it is ground exercises 

 a decided influence on the curling of sections, for the smaller the angle 

 of the cutting edge, /. e. , the narrower the back of the knife in propor- 

 tion to its width, the less the sections will curl. For this reason, as a 

 razor has a narrower back in proportion than most section knives, it 

 does not curl the sections as badly as the latter, and small sections which 

 will curl hopelessly when cut lay an ordinary microtome knife will 

 often not curl at all when cut with a proper razor. 



Cementing Sections to the Slide. — I. In general, an albumen 

 fixative is the best to use when the sections are to be stained on the 

 slide. 



Sections which have to be passed through aqueous fluids after cement- 

 ing are less liable to wrinkle and separate from the slide than those 

 cemented with other substances, notably collodion, and they also take 

 staining fluids much more readily. After cementing with collodion 

 staining is often difiicult, the collodion preventing proper action of 

 the stain, probably because a thin and nearly impervious layer of it- is 

 deposited over the tissue elements. For these reasons an albumen ce- 

 ment is generally to be preferred when the staining is to be done on. 

 the slide, but it presents no advantages over other cements when the 

 staining has been done before sectioning. It has, however, the disad- 

 vantage of becoming stained itself if used too liberally, or if the stain- 

 ing be forced or too long continued. Proper use of the cement and 

 stain will Obviate this in ordinary staining, but it is well to bear it in 

 mind and use collodion when forced methods of staining have to be 

 adopted. Of the albumen formulas, that of Mayer in my experience 

 has the best keeping qualities. It is made by beating together thor- 

 oughly with an egg-beater: White of ^^^t loo grams; glycerine, lOO 

 grams ; sodium salicylate, 2 grams ; and then -filtering. The filtration 

 is very slow, but in course of twenty-four hours sufficient will have 

 passed through to last a long time. 



II. Use the finger to flatten sections on the slide. 

 The finger must be thoroughly cleaned by wiping with a cloth moist- 

 ened with alcohol, as any trace of oil will cause the section to adhere 

 to it, instead of to the slide. Small sections may be flattened by pres- 

 sure after the entire section has been laid on the slide ; but large ones 

 are best smoothed out by taking them up on a small spatula, letting 

 one edge touch the slide, and then following the spatula up by pressure 

 from the finger as it is gradually withdrawn from under the section. 

 If the flattening is thus done gradually and carefully, during the appli- 

 cation of the section to the slide, perfect smoothness may be attained, 

 but if the flattening process is not attempted until the entire section 

 has been laid on the slide, the edges will be apt to adhere, and, instead 

 of its spreading out smoothly, folds will be formed. 



Staining. — I. Adapt the staining to the hardening process which has 

 been employed. 



Tissues hardened by almost any method usually take haematoxylin 



