PRESERVING AND PREPARING PATHOLOGICAL SPECIMENS. 51 



Any form of freezing microtome and either ether or liquid carbonic acid 

 may be used. 



Cullen's procedure is as follows: The frozen sections are put in afive- 

 per-cent watery solution of formalin for from three to five minutes; 

 in fifty-per-cent alcohol for three minutes; in absolute alcohol for 

 one minute. They are now washed in water, stained with hsematoxylin, 

 decolorized in acid alcohol (one-per-cent hydrochloric acid), rinsed in 

 water, contrast stained and dehydrated with eosin alcohol, cleared with 

 creosote or oil of cloves, and mounted in balsam. The tissues shrivel 

 considerably by this method. The disintegration of the sections and 

 especially the considerable shrinkage which they undergo on treatment 

 with alcohol, may be largely obviated by spreading the sections, as they 

 thaw, on an albumin fixative film upon a cover glass or slide see below 

 and conducting the hardening and staining manipulations with the 

 specimen in position upon the glass. 



Hodenpyl ' has found that, when time permits, satisfactory results 

 are secured by placing very small pieces of the fresh tissue for an hour 

 in five -per -cent solution of formalin ; then, after washing out the forma- 

 lin, making frozen sections in the usual way. The sections are now 

 dropped for a moment into a solution of egg albumen of the following 

 composition : 



Egg Albumen .10 



Sodium Carbonate .... ... 1 



Water 30 



Add a lump of camphor to prevent decomposition. 



The sections are now spread on the slide, the excess of fluid being 

 drained off, and are pressed against the glass with a bit of fine cheese 

 cloth. They are finally fixed in place by a short immersion in strong 

 alcohol. The section, now fast on the glass, is stained and mounted, in 

 situ. This procedure, which can be carried out in a little more than an 

 hour, gives a fair chance for an early morphological diagnosis in solid 

 tissues, though the minute structural details are often much altered. 



Fixation : Hardening and Preservation. 



ALCOHOL is the most commonly employed fixative and hardening 

 agent for routine purposes. It is used in the strength of from eighty to 

 ninety-five per cent at first, the pieces of tissue to be hardened not being 

 larger than 1 or 2 c.c. There should be in bulk many times as much 

 alcohol as of tissue to be hardened. A little absorbent cotton may be 

 placed in the bottle to keep the blocks of tissue from sticking to the 

 bottom. After twenty-four hours the alcohol should be renewed. On 

 the third day the tissue is transferred to ninety-seven-per-cent or to 

 absolute alcohol for completion of the hardening, which will usually be 

 within five or six days. 



'Hodenpyl, "A Modification of Cullen's Method of Preparing Fresh Sections for 

 Microscopic Work," Medical Record, March 5, 1898. 



