1890.] MICE(3SCOPICAL JOURNAL. 275 



cut into blocks of a square form, should have its surface dried with 

 clean blotting paper. If it is the intention to cut it by the free-hand 

 method, proceed as follows : A piece of thin lead foil, or a piece of 

 writing paper, should be rolled around one end of a ruler and the end 

 beaten in to form a sort of round case. A piece of paper, or, what is 

 better, a thin card, may be folded up into an oblong dish of sufficient 

 depth to hold the tissue to be cut, leaving plenty of space around it. 

 Pierce the tissue with a fine needle, and run its point through the paper 

 disii into the table, taking care that by this means the block of tissue 

 is supported in the required position. Then melt some paraffin wax, 

 to which a little lard has been added, and when it becomes fluid, and 

 before getting too hot, pour it into the tray, when it will embed the 

 object to be cut. The embedding mass should, when cold, always bear 

 a relative hardness to the embedded tissues, and it can be modified by 

 the addition of lard, to approximate to the condition of the substance to 

 be cut; or paraffin wax of different melting points and varying hard- 

 ness can be selected for the purpose. When the mass is hard, it may 

 be placed in spirit till required, the lead foil or paper being previously 

 removed. If a microtome is used, the melted embedding mass may 

 be poured into its well, and while it is soft the tissue is inserted in the 

 desired position and held there till fixed by the cooling of the mass. 

 There are other methods of embedding, such as steeping the object in 

 gum, and afterwards hardening the gum by immersion in spirit. There 

 is also the plan of filling cavernous tissue, such as the lung, with 

 melted cacao butter, before embedding in paraffine. 



If the student has practised free-hand section cutting, he may take 

 the mass in his hand, wrapped around with a piece of blotting pa- 

 per, and, holding it firmly, steadily cut away the mass in thin slices. 

 The razor must be kept well wet with spirit, and be drawn with a de- 

 cided cut from one side of the tissue to the other ; any pause in the cut 

 resulting in an ugly line across the section. At first there may be a 

 difficulty, but after a little practice a clean, sweeping cut will be at- 

 tained, the section being so thin that every mark on the razor may be 

 seen through it. These thin slices, as they are cut, may be floated into 

 a watch-glass of spirit, where, if sufficientlv thin, they may remain 

 awaiting the next process, while the mass may be returned to the spirit 

 until it is wanted again. % 



After cutting very thin sections with tlic microtome, a trouble veiy 

 frequently arises in transferring them from one solution into another, as 

 in staining and clearing, by their tloubling up. This may be avoided 

 by using the section lifter. This useful piece of apparatus may be 

 made bv bending a narrow band of German silver about half an inch 

 in width, so tliat its lower end forms a flat blade at a convenient angle 

 for passing it under a section. With it lift tlie sections out of the dif- 

 ferent fluids they have to pass through. 



Slides Received. — We desire to return thanks to the donor for the 

 following interesting slide : Diatomacea) : AracJmoidisczis EJircn- 

 beri^/i from Puget Sound, mounted by Mr. A. B. Newman, Fairport, 

 N. Y. 



