430 THE SALIVARY GLANDS, BY E. F. W. PFLUGER. 



been caused to flow by irritation of the gland, it would appear 

 highly probable that these cylindrical epithelial cells also belong 

 to the secretory apparatus. Anatomical examination tells still 

 more strongly in favour of the importance of these structures, 

 since it then appears that the thickness of the wall of the duct, 

 as we advance towards its peripherical distribution, instead of, 

 as might be expected, diminishing, undergoes material increase. 

 The thickening of the wall is, in general, occasioned by the 

 elongation of the cylindric al cells, which, however, never form 

 more than a single layer. Besides this, the wider ducts 

 exhibit more or less strongly marked outgrowths, lined with 

 the same epithelium. If the ramifications of the ducts be 

 traced in a peripherical direction, fine passages are at length 

 met with, having a diameter of O'OIO millimeter, possessing 

 the same epithelial lining as the larger ones, and, if I am not 

 mistaken, terminating in blind extremities; these are the 

 secretory tubules that is, the capillaries of the salivary ducts 

 having the same tenuity as the biliary capillaries, and leading 

 to the alveoli. In a word, these excretory ducts, or salivary 

 tubes, possess diverticula of various form. Not unfrequently 

 they form loops or bend suddenly. 



If we now proceed to the study of the characters of the 



Fig. 76. 



Fig. 76. Transverse section of a fresh salivary tube in diluted chromic 

 acid of one-fiftieth per cent. Magnified 480 diameters. 



columnar epithelium, the cells will be found to possess an 

 average diameter of 0'004< millimeter, and to be of very variable 

 length. The cylindrical epithelial cells are so well defined 

 at their points of contact with each other, and on their free 

 surfaces directed towards the interior of the tube, that they 

 appear to possess a membranous wall; and these walls, towards 



