for Microscopical Examination. 267 



tenuity — are placed in the desired position in the tube, which is 

 then filled up with water, the aperture and contents being protected 

 by placing a small piece of oil-skin over the plate. A thin layer of 

 ice, divided into small pieces, is now placed in the box and on the 

 oil- skin, over this is sprinkled a quantity of pulverized salt, another 

 layer of ice is then added, and again more salt, and so on till the 

 refrigerating mixture is piled over the plate ; finally, the whole 

 mass, machine included, is covered up with the flannel. After an 

 interval of about twenty minutes from the completion of the 

 operation, the tissues will be sufficiently frozen for cutting. All that 

 is now necessary is to remove the ice mixture above the plate and 

 sides of the machine, when the tissue embedded in ice will be 

 exposed ready for cutting. By turning the graduated screw — the 

 thickness of the section depending upon the number of turns or 

 part of a turn given to this screw — the frozen mass will be elevated, 

 a razor is placed at a slight angle on the brass plate and drawn 

 obliquely through the mass projecting from the tube ; the sections as 

 they are cut can be easily floated off the razor into water. The 

 razors used for this machine must be fiat and kept sharp by fre- 

 quent stropping. 



Tissues hardened or preserved in spirit must be placed in water, 

 or a very dilute solution of bichromate of potass to withdraw the 

 spirit, otherwise the freezing of it will be retarded, if not entirely 

 prevented. 



By this method I have cut large and beautiful sections of 

 uniform thickness of softened teeth and bone, of cartilage and 

 tendon, and of hardened and fresh tissues of every description. 

 Further, I may safely say that, if the given directions be rigidly 

 followed, failure will be impossible ; moreover, should you give this 

 method a fair trial (a certain amount of experience in this, as in all 

 things, being necessary), I am confident you will readily concur in 

 Strieker's* assertion : " The simplest and most elegant mode is that 

 of refrigeration." 



* Strieker, loc. cit. 



