10 INTRODUCTION. 



The fibre, also variable in size, is either homoge- 

 neous throughout (connective fibre), or it takes the 

 form of a tube, the walls of which are readily distin- 

 guishable from its contents (muscular fibre, nerve 

 fibre, etc.). 



In the normal state of the human body crystalline 

 substance has, up to the present time, been found only 

 in the internal ear, where it constitutes the otoliths, 

 and in the encephalon ; it is not positively deter- 

 mined that the concretions, composed of concentric 

 layers, which are found in the pineal gland, are crys- 

 talline in their nature. 



