THE PARAFFIN PROCESS 189 



water, they are ready to be mounted upon slides or cover-glasses : 

 slides are by far the best for beginners. The slides (or cover- 

 glasses) must be perfectly clean, and are best kept in methylated 

 spirit until they are to be used, and the spirit not wiped off. 

 Each slide is then inserted separately into the water in an oblique 

 position, and the section moved until it lies over the centre ; the 

 slide is then raised out of the water, and carries the section out 

 with it. 



The excess of water is now to be removed by a piece of 

 blotting or filter paper, and the slide placed in the warm incubator 

 for a few hours. At the end of this time the sections will adhere 

 by atmospheric pressure (like a boy's leather sucker to a stone), 

 and will not come off in the subsequent processes. If an incubator 

 is not at hand the slides may be placed near the fire (protected 

 from dust), and kept at the body temperature or a little higher for 

 a few hours ; the exact temperature does not matter, and no harm 

 will result if the paraffin melts, provided that the section has 

 previously become dry. 



In the older methods of fixing sections to the slides various 

 forms of cements had to be used, and were a great disadvantage. 

 They are quite unnecessary except for sections of the central 

 nervous system ; if these are being dealt with the slide must be 

 coat-ed with a very thin layer of a solution of egg-albumen in water 

 before the section is laid upon it. The process is then exactly 

 the same as before. 



STAINING AND MOUNTING PARAFFIN SECTIONS 



We will suppose that the sections have been cut, flattened out 

 on hot water, and caused to adhere to slides, and shall describe 

 in general terms the steps through which they must be taken 

 before they are ready for examination. In the first place, it is 

 obvious that the paraffin, which permeates all parts of the 

 section and surrounds it on all sides, must be removed, and 

 this is done by pouring xylol, benzine, or turpentine upon it. 

 At least two supplies of the fluid should be used, and it should 

 be allowed to act for at least two minutes, the slide being 

 rocked all the time. We have now removed the paraffin, and 

 the next step is to remove the xylol or other solvent ; this is 

 done by means of absolute alcohol. At least two lots should be 

 used, and it should be allowed to act for two minutes. The slide 



