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alcohols of different strength, 60, 80, 96X and absolute, 

 in each of which the tissue remains for 24 hours. 



Cutting sections. As already stated the tissue 

 which has been hardened in alcohol may be cut directly 

 and sections can thus be obtained which are fairly good. 

 Another method for obtaining sections is to employ the 

 freezing microtome, in which case the alcohol is first re- 

 moved from the tissue by placing the pieces in water. 

 This is accomplished in cold water in 4-8 hours, depend- 

 ing: on the size of the pieces. Warm water about 38 C. 

 will remove the alcohol more rapidly, in 1 to 2 hours. 

 The tissues can then be frozen and sections cut. The 

 knife should be kept moistened with water and the sec- 

 tions are transferred at once to water. 



Undoubtedly the most satisfactory method of prepar- 

 ing sections is to first imbed the hardened tissue either in 

 celloidin, or in paraffin. Either method gives excellent 

 results. The method for imbedding in paraffin which is 

 usually employed in the laboratory is briefly as follows : 



The hardened tissue is placed in absolute alcohol for 

 24 hours; then for 4 to 5 hours in chloroform, then in a 

 chloroform-paraffin solution over night. The pieces are 

 then placed in paraffin which melts at about 42 C. and kept 

 in a water air-bath at a temperature of about 50 for 24 

 hours. From this the tissue is transferred to hard paraffin 

 which melts at about 48 C. This may be obtained by 

 taking equal parts of 42 and 56 paraffin. After 24 

 hours the piece of tissue is "blocked.-' . Two glass L's are 

 fitted together so as to make a trough of suitable size, and 

 this then filled with melted paraffin (48 C.) The piece of 

 tissue is transferred by means of a pair of forceps, slightly 

 warmed, to the center of the block and the whole allowed 

 to cool. The solid block, if necessary, is then trimmed, 

 fastened to the microtome and sections cut with a dry 

 knife. 



From absolute alcohol the pieces of tissue can be 

 placed first in toluene for 24 hour,s; then in a mixture of 



