NERVOUS TISSUE. 423 



sertion of the tendons abnormally near to the belly of the muscle. 

 Hence the propriety of dividing the tendons, and bringing the bones 

 into their normal relations, in such cases; after which, the former 

 assume the normal length by a new formation of collagen ous tissue 

 between the divided extremities. 



The vaginal sheaths of the tendons, especially of the extensors of 

 the fingers, are liable to dilatations and accumulations of the syno- 

 vial fluid, forming protrusions called ganglia. The most common 

 seat of the ganglion is on the dorsum of the wrist. 



The sy no vial sacs of the muscular system (burs mucosae) are also 

 liable to inflammation, and consequent distension, from the fluid 

 they contain. The affection usually termed "housemaid's knee" is 

 an inflammation of a synovial sac, not connected with the muscular 

 system, but existing between the patella and the skin covering it. 



CHAPTER X. 



NERVOUS TISSUE, AND THE STRUCTURE OF THE NERVOUS 



SYSTEM. 



SECTION I. 

 THE NERVOUS TISSUE. 



Two forms of the nervous tissue are to be described : 



I. The fibrous or tubular nerve-tissue. 

 II. The vesicular or cellular (nerve-cells). 



I. FIBROUS OR TUBULAR NERVE-TISSUE. 



This form of nerve- tissue is termed tubular, because, when de- 

 veloped in the highest degree, it presents the form of tubes inclosing 

 a fibre. In other cases, however, the tube is wanting, and then the 

 term "fibrous" is more appropriate. The latter are far more minute 

 than the former ; and hence these two forms have been called by 

 Kolliker the coarse and the fine nerve-fibres. (Fig. 272.) There is 

 also a medium size, averaging about the ^Vir of an inch in dia- 

 meter. 



The coarsest nerve-fibres are even y^^ of an inch in diameter; 

 while the finest have only ^ this diameter, or ^^-Q-Q of an inch. 



