176 COLLODION SECTIONING \_CH. VII 



specimens may be mounted in glycerin, glycerin jelly or balsam. Glycerin jelly 

 is the most satisfactory, however. 



FIG. 146. Pfeiffer' 1 s preparation microscope with erecting prism between the 

 objective and ocular (Leitz ; Wm. Krafft, New York}. 



THE PREPARATION OF SECTIONS OF TISSUES AND ORGANS 



\ 265. At the present time there are three principal methods of obtaining 

 thin sections of tissues and organs for microscopic study. These methods are : 

 The Collodion Method, the Paraffin Method, and the Freezing Method. Each of 

 these methods has its special application, although the collodion method is per- 

 haps the most generally applicable, and the freezing method the most restricted, 

 and is used mostly in pathological work where rapid diagnosis is necessary and 

 the finest details of structure are not so important. With the paraffin method the 

 thinnest sections may be made, and in some ways it is the most satisfactory of all. 

 A good microtome is of great aid in sectioning. 



266. The Collodion Method. In sectioning by this method the tissues are 

 first hardened properly and then entirely infiltrated with collodion, and the collod- 

 ion hardened. It is not removed from the tissue, since on account of its transpar- 

 ency it does no harm. 



\ 267. Fixing and Hardening the Tissue. Any of the approved methods 

 of hardening and fixing may be employed. A good general method which is 

 applicable to nearly all of the tissues and organs is that by Picric-Alcohol. P'or 

 the preparation of the solution see (\ 333). A small piece of tissue or organ not 



