APPENDIX. 28l 



It is preferable to have a good microtome. The best is that of Minot. Very 

 satisfactory sections can be cut with the various types of student microtomes, costing 

 from $12 to $20. 



(In using a hand microtome, a razor with a flat edge is necessary. After experience, 

 sections thin enough for histological but not for bacteriological examination can be 

 made.) 



If the piece of tissue is properly dehydrated and imbedded, thin sections (3 to IOM) 

 should be easily obtained, provided the knife be sharp. One advantage about the 

 paraffin method is that it is only necessary to have a small part of the blade in 

 proper condition. With celloidin the entire cutting edge must be perfect. Having 

 cut the sections, they should be dropped on the surface of a bowl of warm water 

 (45 C.). This causes the section to flatten out evenly. 



Decalcification. This is best accomplished by fixing in 10% formalin for 24 

 hours, then placing a small piece of the bone (not exceeding one-half inch square 

 and one-fifth of an inch thick) in concentrated sulphurous acid. 



This decalcifies in about 24 hours. Wash thoroughly in alkaline water and then 

 in tap water. Pass through alcohols and xylol and imbed and section as before 

 described. 



To Stain Sections. It is first necessary to affix the section to a slide or cover- 

 glass. 



To attach the section firmly to the slide, so that it will not become detached in 

 subsequent treatment, pick up a section on a strip of cigarette paper. 



A sheet of cigarette paper is cut into about five pieces (1/2 x i 1/2 ins.). 

 Inserting the strip of cigarette paper under the section, it is easily lifted up out of 

 the water. Then apply the slip of cigarette paper, section downward, to a perfectly 

 clean slide. Blot with a piece of filter-paper, then strip off the piece of filter-paper 

 leaving the section smoothly applied to the slide. Next place in the 37 C. incubator 

 for twelve to twenty-four hours and the section will be found to be so firmly attached 

 that it will not be dislodged by subsequent treatment. 



For Immediate Diagnosis. Take a loopful of albumin fixative (white of fresh 

 egg, 50 c.c.; glycerin, 50 c.c.; sodium salicylate, i gram) and deposit it on a cover- 

 glass. Now take up a loopful of 30% alcohol (i drop of 95% alcohol and two drops 

 of water) and applying it over the albumin fixative, smear out the mixture uniformly 

 over the cover-glass. 



2. Pick up a section on a strip of cigarette paper and apply it to the prepared sur- 

 face on the cover-glass. Blot with gentle pressure with a piece of filter-paper over 

 the strip of cigarette paper, and strip off this latter, leaving the section attached to 

 the cover-glass. 



3. Now, turning the flame of theBunsen burner down very low or with a small 

 alcohol flame, we hold the cover-glass in a Stewart's forceps, section side up, over 

 the flame and slowly lower it until the paraffin is observed to melt. This shows a 

 temperature of about 50 C. The section is fixed by the coagulation of the albumin 

 at about 70 C. To obtain this temperature lower the cover-glass still more, and the 



