6o Neurological Technique 



If a cover-glass is used, the hardening of the mounting 

 medium is much retarded, and the consequent long period of 

 diffusion currents causes the metal deposits upon the elements 

 to break up, and the preparation becomes worthless. The xylol 

 may be omitted. 



Sections may be mounted under a cover-glass with results 

 which are sometimes permanent, by first applying heat to the 

 balsam to quickly drive off the solvent oil. After covering the 

 sections with balsam, place the slide in a thermostat at 100° C. 

 for about one-half hour, or carefully heat it over a bunsen flame' 

 for 4 or 5 minutes, and then, before the balsam cools, put on 

 a large cover-glass and press it down to drive out the bubbles 

 and to make the layer of hardened balsam as thin as possible. 

 It is better to omit cover-glasses, however, except when it is 

 necessary to study the preparations under high power. 



Without the cover-glass the balsam tends to leave the sec- 

 tions and run out over the slide, thus requiring several renewals 

 during the first 12-24 hours. This may be obviated to some 

 extent by first wiping the free surface of the slide about the sec- 

 tions with a cloth wet in absolute alcohol before putting on the 

 balsam. 



APPLICATIOW TO MATERIAL PRESERVED IN TEN PEIR CENT. FORMALIN. 



1. Remove the brain and spinal cord, subdivide them, and 

 place in a tightly closed vessel containing 8— 10 volumes of 10 

 per cent, formalin (A, 2). In this fluid the tissues may remain 

 indefinitely. It is not necessary to divide the nervous system into 

 small pieces. Good results have been obtained from the cortex 

 of an ' adult human cerebral hemisphere preserved entire, and 

 also after it had been kept in the formalin solution for more 

 than a year. It is better, however, to divide somewhat, in order 

 to hasten the fixation. 



2. On occasion, any time after 3 or 4 days of fixation, 

 reniove small pieces of the tissue (4-5 mm. thick) from the 

 regions required and place them in a vessel containing 10-20 



• HUBER, Anat. Anz., Bd. VII, 1892. 



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