4O THE MICROSCOPIC PREPARATION. 



section is then taken up on a cover-slip coated with a very thin layer of 

 Mayer's albumen fixative. During this procedure the cover-slips are held 

 by forceps, and the sections are guided by means of a small camel's-hair 

 brush. When all the sections have thus been placed on cover-slips they 

 are placed for four to six hours in a warm oven maintained at 30 to 

 35 C. 



Removal of Paraffin. Before paraffin sections, either fixed or 

 loose, are subjected to further manipulation, the paraffin surrounding the 

 tissues must be removed. This may be done by means of several agents 

 having a solvent action on paraffin, such as xylol, toluol, oil of turpen- 

 tine, etc. After the paraffin has been dissolved, the sections are trans- 

 ferred to absolute alcohol and by this means prepared for further treatment 

 with aqueous or weak alcoholic solutions. 



Dextrin Method of fixing Paraffin Sections. This method is 

 to be recommended for class-room purposes where 30 to 50, or even 

 more sections need to be stained at one time. 



The following solutions are kept on hand : 



Solution i : 



A solution of equal parts of white sugar 



and boiling distilled water 300 c.c. 



A solution of equal parts of distilled water 



and dextrin 100 " 



Absolute alcohol 200 " 



Mix the sugar and dextrin solutions in a mortar, and add very slowly, 

 while constantly stirring, the absolute alcohol ; filter through fine muslin. 

 Keep in a wide-mouthed bottle through the cork of which there has been 

 placed a broad camel's-hair brush. 



Solution 2 : 



Photoxylin IO gm. 



Absolute alcohol looc.c. 



Ether 500 " 



The sections to be stained are cut and arranged on a clean piece of 

 paper. A clean glass plate is coated with a thin layer of solution No. i. 

 The sections are arranged on this and pressed against the plate with the 

 finger. The plate is now placed in a warm oven (temperature 40 C.), 

 where it remains for several hours. The plate is then warmed over a 

 flame until the paraffin of the sections begins to melt and is then placed 

 in a tray containing xylol, where it remains until the paraffin is dissolved. 

 It is then transferred to a tray containing 95^ alcohol and the xylol re- 

 moved. The plate is next taken from the tray and the alcohol drained 

 off. The plate is now covered with a thin layer of solution No. 2, and 

 set aside, at an angle, until the photoxylin dries. The plate is now 

 placed in the staining fluid, in which, or in the water used in washing off 

 the staining fluid, the thin layer of photoxylin, to which the sections ad- 

 here, separates from the plate. This thin film may now be treated as 

 one section and carried on in this form through the several stages of 

 staining and clearing until the process is completed. The individual 

 sections are cut from the film with scissors. 



Celloidin preparations can not be fixed to the slide with the 

 same degree of certainty, although many sections may be treated at one 

 time. The celloidin sections can be collected in their sequence on strips 

 of paper by gently pressing such a strip, on the blade of a knife, onto the 



