NERVE-TISSUE. ICQ 



latter becomes attached to the surrounding struc- 

 tures by a layer of connective tissue. Finally, when 

 we arrive at the larger nerve-trunks, we find that in 

 each the connective tissue presents itself in three 

 ways : 



1. It forms a distinct sheath, which, although the 

 analogue of Henle's sheath, has a much more com- 

 plicated structure, and is called the lamellar sheath. 

 This is composed of several concentric lamellae, each 

 of which is formed of a fenestrated membrane of 

 fibrillar connective tissue containing granules of 

 elastic-tissue substance, and covered with endothelial 

 cells. The lamellae are connected by oblique fibres, 

 which pass from one to the other, binding them more 

 or less firmly together. The whole forms a compact 

 sheath, closely investing the fascicle of nerve-fibres. 



2. Outside of the lamellar sheath, and joining it 

 to adjacent structures to neighboring nerve-fasci- 

 cles, if the nerve-trunk is composed of several of 

 these, as is the case in many large nerves we find 

 loose fibrillar connective tissue with flattened, ir- 

 regular-shaped cells like those found in the loose 

 subcutaneous connective tissue reinforced by elas- 

 tic fibres, and often containing fat-cells. The fibril- 

 lated and elastic fibres, especially in the immediate 

 vicinity of the lamellar sheath, usually run in a di- 

 rection approximately parallel with the axis of the 

 nerve. This tissue is called the peri-fascicular connec- 

 tive tissue. 



