342 THE AMERICAN MONTHLY [Nov. 



In a few iiunutes, 15 or 20 at most, the pieces take a beau- 

 tiful color varying from vivid red to deep violet. Too 

 long warming will produce a black and granular de- 

 posit, which prevents observation. By experiment we 

 reach the proper point. After either method, the piece is 

 placed in strong alcohol. . . . Make sections perpen- 

 dicular to the surface (in gum) ; mount in glycerine. 



PaccinVs corpuscles. — It is well to study these first in 

 mesentery of a kitten. Spread out a j)ortion of the mem- 

 brane taken from near its point of insertion, and search 

 for the corpuscles with a low power. When a few have 

 been found . . . free them by needles from connective 

 tissue and fat cells, and put them in a silver nitrate, 1 to 

 300. When impregnated with it, wash and mount in 

 glycerine. . . Into a very fresh human finger, in the 

 course of the nerves inject with a hypodermic syringe 

 1 per cent osmic acid. After cutting the skin along the 

 course of the nerve, take one of the pieces and dissect it. 

 In the midst of the fatty layer, colored black, we see 

 Paccini's corpuscles colored a clear translucent yellow. 

 Collect them, free them from the debris of connective 

 tissue, and plunge them into a 1 per cent solution of picro- 

 carmime for 24 hours. Wash them, harden by alcohol. 

 With a little practice, longitudinal and transverse 

 sections may be made by imbedding in elder pith. Or 

 they may be imbedded more easily in paraffin, as follows. 

 From the 90° alcohol, they are placed in absolute alcohol 

 (12 hours), then in oil of cedar for 12 hours, finally in 

 paraffin. . . The paraffin should be dissolved from 

 the sections by benzine ; mount in balsam. To see the 

 capillary net work in the corpuscles inject the'finger with 

 the Prussian blue gelatine mass. 



To he Continued. 



