108 The Mickoscope. 



fixing the nerve-ghred on the point of a needle, place it in the center 

 of the drop, and with the other needle, gently strip ofP threads from 

 it. As the fibers run longitudinally the teasing should take the same 

 direction. Do not pick off transverse pieces, nor break, any further 

 than possible, the delicate, longitudinal fibrils. After a number 

 of these fibrils are obtained, see if it is not possible to still further 

 tease them into more delicate ones. When this process is complete, 

 separate and straighten out the fibrils, add a little water and lower a 

 cover-glass over them, 



This lowering of the cover-glass requires a little practice. 

 Do not drop it down with a splash. Take it up with the diameter 

 extending between the index finger and thumb of left hand (if right- 

 handed), and place one edge on the slide just in contact with the 

 edge of the fluid. With the right hand, palm downward, take a 

 needle-holder and support the cover by passing the needle under 

 the upper . edge. Now gently lower the cover, but no faster than 

 the liquid is enabled to fill up the successive angles formed by the 

 two glasses. This will avoid the forming of air bubbles — les betes 

 noirs of fastidious microscopists. When bubbles appear they do so 

 at the advancing edge of the liquid. In this case they can often be 

 dispelled by raising and lowering the cover glass a little, with a 

 slightly jerking motion. The cover down, take up with a blotter the 

 superfluous fluid around its edge, and the specimen is ready for 

 examination. 



Using a one-fifth objective, observe the fibers — many of which 

 will be distinctly separate — their whitish, varicose appearance. 

 Here and there the dark contour of the neurillemma will be visible 

 and occasionally a node of Ranvier. 



(Note. — As these lessons are only for the teaching of technique, 

 the reader will do well to cons^^lt works on histology where descrip- 

 tions of tissues are desired.) 



Now irrigate with sulphuric ether. This is done by placing a 

 few drops of ether on one edge of the cover and a blotter at 

 the opposite edge. As the water is drawn off by the latter the ether 

 replaces it. As ether evaporates rapidly it should be applied very 

 freely. When the process is complete examine again, and it will be 

 seen that the axis cylinders are now visible in many places: the 

 medullary substance, which before obscured them, being of a fatty 

 nature is now dissolved by the reagent. 



Tease out a thin, longitudinal strip of striated muscle in the 

 manner described for nerve and in the same solution. Observe the 

 distinct and regular transverse striations of the fibers— a unique 



