DISTRIBUTION OF THE NERVES IN THE SALIVARY GLANDS. 433 



The proper excretory ducts (Ductus Whartonianus, Stenonianus, 

 etc.) are generally admitted to be lined by an epithelium, con- 

 sisting of a single layer of short cylindrical cells. Boll, how- 

 ever, describes the epithelium as composed of tesselated cells. 

 The wall is strengthened by fibres of connective tissue, with 

 numerous elastic fibres and membranes, as well as by smooth 

 muscular fibre cells. 



4. DISTRIBUTION OF NERVES IN THE SALIVARY GLAND. 

 The nerve tissue of the salivary glands consists of ganglion 

 cells and fibres. The latter are composed both of medullated, 

 which constitute the greater number, and of pale nerves. 



Three different kinds of pale nerves may be distinguished. 



a. Fasciculi of extremely delicate transparent fibres, pre- 

 senting the characters of axis cylinders, and invested with a 

 sheath of connective tissue, containing nuclei. Were it re- 

 quisite to adduce any proofs of the nervous nature of these 

 fasciculi, it might be pointed out that these pale fibres form 

 from time to time large fusiform varicosities, consisting of nerve 

 medulla, characterised by its double dark contour. The pale 

 fibre between two such varicosities differs in no respect from 

 that lying in their immediate proximity. The above feature, 

 however, renders it probable that these pale fibres conceal a thin 

 layer of nerve medulla between the axis cylinder and .the 

 sheath. At the same time, neither a special investing sheath 

 nor nuclei can be demonstrated around the individual primitive 

 fibres, as indeed follows from what has been above stated, and 

 these consequently, in the fresh condition, possess the appear- 

 ance of naked axis cylinders. 



6. A second kind of pale nerve fibre found in the salivary 

 glands I shall denominate gelatinous fibres. They consist ap- 

 parently of bands of finely granular protoplasm, lying in a 

 sheath of connective tissue, in which are nuclei, and presenting 

 exactly the same appearance and behaviour as the protoplasm 

 of the large ganglionic cells of the glands. Such gelatinous 

 fibres may be observed to leave the ganglion cells, and hence 

 are unquestionably of a nervous nature. They are probably 

 composed of fasciculi of extremely fine varicose fibrilfce, which, 

 lying in close apposition, give the impression of a finely granular, 



