464 SPECIAL HISTOLOGY. 



the racemose mucous glands, that it would be quite superfluous to enter 

 into any detailed description of them* They are compound racemose 

 glands, and they might be regarded as aggregations of numerous mucous 

 glandules. In fact, the primary and secondary lobulations which are 

 observed in these glands correspond, the latter to the entire mucous 

 gland, the former to its lobes. The secondary lobulations then become 

 united into still larger groups, and a certain number of these constitute 

 the whole gland. The excretory ducts correspond with the number of 

 the lobulations of the gland ; they are more or less branched, and in 

 their final relations resemble those of the mucous glands. 



The more intimate structure of the salivary glands presents nothing 

 remarkable. The glandular vesicles have about the same diameter 

 0-016-0-024-0-03 of a line, in all three descriptions of glands ; they are 

 as variously formed as in the mucous glands, and proceed in a similar 

 manner from the excretory ducts. Their membrana propria frequently 

 presents a double contour, and is, internally, always clothed with a 

 pavement epithelium, whose cells of 0*005 0*008 of a line have a single 

 nucleus, and may be obtained in beautiful series by coarsely crushing 

 the gland ; they are distinguished by their greater proportion of fatty 

 granules and pigment granules from those of most mucous glands, 

 whence the glandular vesicles themselves present a somewhat dark 

 appearance. Here, also, acetic acid makes the contents of the cells 

 turbid, the addition of an excess even not restoring their clearness, and 

 it is not therefore advisable to make use of it in our examinations ; a 

 very dilute solution of caustic soda, which allows the epithelial cells to 

 be seen in situ, is more to be recommended. 



The excretory ducts of the salivary glands possess a single layer of 

 cylinder epithelium, whose cells measure 0*016 of a line in length. The 

 remaining portion of the wall, which is very thick in Stenons duct, but 

 much thinner in the others, has a dense, solid structure, and consists of 

 connective tissue, with a very close network of fine, and moderately 

 thick, elastic fibres. It is only in Whartons duct that we find, exter- 

 nal to the epithelium, and to a double layer of elastic membranes whose 

 elements are disposed transversely and longitudinally, a thin stratum of 

 smooth muscles, which, however, can only be demonstrated and isolated 

 with very great difficulty. They are disposed longitudinally, have short 

 nuclei of 0*004-0*006 of a line, at most 0*008 of a line, and are covered 

 externally by a layer of connective tissue with elastic fibres. 



The vessels of the salivary glands are very numerous, and present the 

 ordinary structure. The capillaries have a diameter of 0*003-0*004 of 

 a line, and form broad networks in which the glandular vesicles are im- 

 bedded, so that each vesicle receives its blood from several directions. 

 A considerable number of vessels are distributed also to the excretory 

 ducts. Lymphatics are found in the salivary glands, but their internal 



