FIXATIVES AND SUBSEQUENT TREATMENT OF SECTIONS. 6 1 



To Fix Paraffin Sections on a Slide. There are several "fixa- 

 tives" for serial sections, but the following will be found the 

 most useful. 



(1.) Collodion and Clove-Oil. Mix one part of collodion with 

 three parts of clove-oil. By means of a brush paint a thin layer on 

 a slide, and on it place the sections. Heat gently over the flame of 

 a lamp, to fix them firmly and drive off the clove-oil. 



(2.) Albumen and Glycerine (P. Mayer}. Mix filtered fresh 

 white of egg with an equal volume of glycerine, add a little car- 

 bolic acid or morsel of thymol to prevent putrefaction. White 

 of egg filters very slowly. A very thin layer is painted on the 

 slide, and made smooth by means of a clean glass rod, which is 

 thus prepared to receive the sections. The sections are flattened 

 on the albuminised surface by means of a fine brush, care being 

 taken that no air-bubbles remain under the sections. Warm the 

 slide to a temperature just sufficient to coagulate the albumen 

 (70 C.). This may also be done by holding the slide for a few 

 seconds over a jet of steam. 



Such substances as acids and alkalies which dissolve the 

 albumen must not be applied to the sections, nor must the sections 

 be stained with such substances as picrocarmine, which also 

 dissolve the albumen. 



(3.) Method of Gaule. This method depends on capillary attrac- 

 tion. The slide is moistened with water or weak spirit, and on 

 this the paraffin sections are carefully spread out. The surplus 

 spirit or water is removed by blotting-paper, and the slide placed 

 in a thermostat at 50 C. for twenty-four hours. Sections so dried 

 are heated for a moment above the melting-point of the paraffin, 

 and are then firmly fixed on the slide. 



To Remove Paraffin from the Sections. Sections of tissues 

 soaked and embedded in paraffin and fixed on a slide are placed in 

 turpentine, toluol, or xylol. The extraction of the paraffin requires 

 some time, and takes place more rapidly when the temperature is 

 raised. The slides may be fitted into a zinc framework and 

 lowered into a bath of turpentine or toluol. Clove-oil must not be 

 used if collodion and clove-oil have been used as a fixative. In 

 that case clarify with creosote and turpentine. The turpentine 

 dissolves out the paraffin. 



After this, if the tissue has been previously stained in bulk, 

 before it was embedded, drive away the turpentine with xylol or 

 clove-oil, and mount the section in balsam. 



If, however, the sections are from an unstained tissue, after 

 dissolving out the paraffin with turpentine, the latter must bo 

 displaced by absolute alcohol, and the slides are passed through 

 alcohols of various strengths and then into water, i.e., provided the 



