TEEMINATIONS OF NERVES IN TORTOISE-SHELL. 565 



to be found in this region ; and one is forced to conclude that 

 owing to their peculiar situation — perhaps on account of the 

 pressure of the hard scutes placed immediately above them — 

 the medullated nerves are replaced by axis-cylinders, enclosed 

 and protected by the sheaths of modified connective tissue 

 just described. 



These modified nerve-fibres can be traced back a little way 

 into the bone, and no doubt ultimately pass into the ordinary 

 medullated nerves found so plentifully on the inner surface 

 of the carapace. Under the scutes they freely branch, 

 becoming smaller and smaller, and ultimately terminate in the 

 lower epithelial cells of the tortoise-shell. We have, therefore, 

 medullated fibres passing from the central nervous system to 

 the bone of the carapace and plastron, these then pass into the 

 medullary nerve-fibres seen under the scutes, from which, as 

 we shall presently see, fine terminal naked axis-cylinders run 

 into the scutes. 



The final intra-epidermic termination of the nerves was 

 never seen in any of the sections, for the softening of the 

 tissue previously to its cutting prevented their subsequent 

 demonstration by staining agents. The nerve endings may, 

 however, be demonstrated by another very simple method. 



The scutes from a recently killed tortoise are removed in 

 pieces with a sharp scalpel, care being taken to keep attached 

 to their under surfaces as much as possible of the subjacent 

 connective tissue ; and it will be found advisable before doing 

 so to remove as much as possible of the dense outer part 

 of the scute. In this way one can obtain thin and fairly 

 transparent pieces of tissue, consisting of the lower layers of 

 the tortoise-shell and the tissue connected with it. These are 

 placed in absolute alcohol 2 parts, and distilled water 1 part, 

 and after twelve hours are thoroughly steeped in distilled water 

 until every trace of alcohol is removed. The tissues are then 

 placed in a solution of hsematoxylin until they are sufficiently 

 stained ; they may then be mounted in balsam, the connective 

 tissue or deeper layer being above the epithelium and next 

 the cover-glass. 



