Embedding Tissues and Section-cutting. 75 



and cheapest freezing microtome, and it can be obtained 

 from any optician. 



(1) Cut a slice of the specimen about J inch thick, in 

 the direction you wish to make the section. 



(2) Place in water for an hour to remove the alcohol. 



(3) Transfer to a mixture of gum-water 5 parts, saturated 

 watery solution of loaf-sugar, 3 parts, and allow it to soak 

 in this for about twelve hours ; or, if a few drops of carbolic 

 acid are added to the mixture, tissues may remain in it for 

 months without harm. 



(4) .Clamp the microtome to a table, fix the ether spray 

 in its place, and fill the bottle with ether. Methylated ether 

 S.G. '720 will do. 



(5) Put a little gum-water- not gum and syrup on the 

 zinc plate of the microtome, and place the tissue in it. 

 Commence working the bellows, and as soon as all the gum 

 has frozen add some more and freeze again, and so on 

 until the tissue is completely covered and frozen into a 

 solid mass. 



(6) The best instrument for making the sections is the 

 blade of a carpenter's plane. Hold it firmly in the right 

 hand, and work the microtome screw under the machine 

 with the left. Plane off the sections as quickly as possible. 

 They should all collect on the plane iron. If they roll up 

 or fly off, the tissue is frozen too hard, or there is not 

 enough syrup in the gum. If the former is the case, allow 

 the mass to thaw a little ; if the latter, add some more 

 syrup to the gum mixture, and soak the tissue again. 



When the sections are cut, place them in a saucer of 

 water, which must be changed several times until all trace 

 of gum is removed. Water that has been boiled and 

 allowed to cool will remove the gum sooner than cold 

 water. When quite free of gum, the sections may be 

 bottled up in methylated spirit until required for staining. 



Embedding in Celloidin. Dissolve celloidin in equal 

 parts of ether and absolute alcohol until the solution is as 

 thick as oil. 



