108 NERVOUS TISSUE. 



Kolliker ; while the nerve-pulp protrudes either at the extremities 

 of the torn fibres, or through the sheath, which bursts at the 

 point of contraction, in the form of vesicles and granules arid more 

 or less sharply defined light or dark globules. It is only in rare 

 instances that the gelatinous swelling and final disappearance 

 of the axis-cylinder can be distinctly traced. 



When nerve-preparations which have previously been boiled 

 with alcohol or ether are suffered to remain for a considerable time 

 in a dilute solution of soda, the nerve- tubes appear to be consider- 

 ably contracted, and to become almost perfectly pale; there is 

 very little indication of any granulation in them, and the appear- 

 ance presented to us is that of contracted nerve-sheaths from 

 which the contents were entirely removed. 



The nerve-cells swell in a dilute solution of soda and become 

 paler ; in the meanwhile the cell-membrane is frequently rendered 

 more distinct (Kolliker), but after a time the nucleus wholly dis- 

 appears. When the grey substance of the brain, or any other 

 nervous substance rich in cells, is exposed to the action of a dilute 

 solution of soda, the cells, that is to say, both the walls and the 

 nuclei, wholly disappear, leaving only a more or less finely granular 

 substance. 



When the nerve-fibres have lain for a prolonged time in a 

 concentrated solution of potash, the whole mass becomes converted, 

 on being well shaken, into a white emulsive fluid ; under the 

 microscope, in addition to simple and double outlined, light or 

 dark vesicles, there appear the most complicated forms of this fat- 

 like matter. Although baton-like bodies having double contours, 

 or long filaments varicosely swollen at individual points, become 

 visible, these cannot be regarded by any one who observes them 

 attentively, as the remains of nerve-fibres, for both the sheaths and 

 the axis-cylinders are completely dissolved on prolonged digestion. 

 But when a concentrated solution of potash is added to a fresh 

 preparation of animal or vegetative nerve-fibres, the contents of the 

 individual tubes become granular, the double contours of the 

 animal fibres disappear, and no trace of the axis-cylinder remains. 

 If the preparation is suffered to remain in the air for a pro- 

 longed time (until it absorbs water), or if water be added, the 

 outlines disappear gradually, but completely, leaving only serially 

 arranged granules which indicate the former position of the fibres. 



When fresh preparations are treated with a concentrated 

 solution of potash, the nerve-cells become slightly contracted, 

 their contents exhibit a more granular appearance, and neither 



