18 CUTTING A ND MO UNTING TISS UES. 



strengths. A Schulze's apparatus is to be recommended for this 

 operation. If alcohol has been used for hardening, the disagreeable 

 process of washing can be omitted. The alcohol is now replaced 

 by some solvent of paraffine, as chloroform, tui-pentiue, clove or 

 cedar oil, xylol, or benzol. Chloroform is readily miscible with 

 paraffine, but is not very penetrating, and therefore requires a 

 much longer time for clearing than some of the other solvents. 

 Further it must be entirely driven off before sectioning, otherwise 

 the paraffine will be too soft to support the tissue. Turpentine is 

 recommended by Mohl, but this is often harmful to delicate struc- 

 tures. Cedar oil is perhaps the best of any of the agents for pene- 

 trating and clearing. Should turpentine be used, as Mohl recom- 

 mends, the tissue is first placed for a few hours in a mixture of 

 equal parts of alcohol and turpentine and an equal length of time 

 in the pure agent, then after a few hours it should be removed, 

 placed in a cold saturated solution of paraffine in turpentine, after 

 which it is placed in a bath of equal parts of turpentine and para- 

 ffine, kept at the temperature of 30 to 40 C. In a few hours the 

 tissue is transferred to pure paraffine, with a melting point of 

 50C., and in this it is allowed to remain until thoroughly satur- 

 ated with the imbedding mass. With cedar oil the object is trans- 

 ferred directly from the clearing agent to pure paraffine and left 

 there until infiltrated. The time required for infiltrating any object 

 depends upon the nature of the tissue. For some objects an hour is 

 sufficient, while with others one or two days is required. After the 

 object is infiltrated it is placed in a paper box and pure melted 

 paraffine is poured over it. A convenient form of a paper box can 

 be made as follows: 



Take a piece of stiff paper of the proportions shown in Fig. 

 2 and fold inward along the lines A A and B B, one third of 

 each side. Repeat the operation with the ends, folding them along 

 the lines C C and D D. At each corner fold inward on a line 

 bisecting the angle formed by the lines A A and B B, etc., allowing 

 the crease to follow the lines E E, E'E', etc. Tben turn up the 

 sides and ends until they are at right angles with the bottom, and 

 bring back around the ends the portions projecting at the corners. 

 Fold outward the portion projecting above the sides of the box 

 and press it firmly against the end thus holding all the parts in place. 



