432 THE SALIVAKY GLANDS, BY E. F. W. PFLUGER. 



or disappearance of their processes, and the assumption of a 

 polygonal form, approximate closely to the flattened epithelium 

 found in the alveoli. This similarity also extends to the cell 

 contents and to the nucleus. 



Besides these extremely fine processes of the columnar 

 cylinder cells, resembling the fibrils proceeding from the axis 

 cylinder of a nerve, others of greater thickness, and of high 

 refractive power, may be observed to be given off from their 

 sides. The significance of all these processes will be hereafter 

 discussed at greater length. 



Lastly, as regards the dimensions of the calibre of the tubes, 

 it is found that they vary from a diameter of 0*030 millimeter 

 or less to a size easily recognisable with the naked eye. The 

 enlargement is essentially effected by increased diameter of the 

 lumen, and to a less extent by increased length of the columnar 

 epithelium. I have met with such canals in the interior of 

 the glands of the dog, the lumen of which had a diameter of 

 O'l millimeter or more. 



Besides the salivary tubes, other tubes are found in the 

 salivary glands, varying considerably in diameter, and lined by 

 a small description of tesselated epithelium, that generally 

 diminishes with the bore of the tube. These may be injected 

 through the ordinary excretory ducts, as well as through 

 the salivary tubes, and ultimately form by their ramifications 

 passages which have only a diameter of O'OOT millimeter or 

 less, and are lined by a very small-celled pavement epithelium. 

 These passages constitute without doubt, excretory ducts pro- 

 ceeding from the alveoli, and form a stage in that developmental 

 metamorphosis of the gland which exists even in the adult. 



Whether the salivary tubes, which are continuous with these 

 excretory ducts lined by pavement epithelium, communicate 

 with the alveoli, and in what way this communication, if pre- 

 sent, is effected, demands further investigation. I know for a 

 fact that a mosaic of salivary cells may lie in immediate juxta- 

 position to columnar epithelium; but it is very rare for the 

 canal of a salivary tube to be directly continuous with a canal 

 which is lined with salivary cells. I am of opinion that the 

 communication between the salivary tubes and the alveoli is 

 effected by means of very fine passages (salivary capillaries). 



