460 



MANUAL OF HISTOLOGY. 



245. 



Until very recently, the salivary glands received but little attention from 

 a histological point of view, but a step in the right direction has lately 

 been made in the interesting studies ofPftiiger, Gianuzzi, and Heidenliain, 

 followed by a number of other observers. 



These organs may from their form be regarded, to a certain extent, as 

 highly developed and complex mucous glands. 



The submaxillary gland presents in various mammals, according to its 

 cellular contents, considerable and important physiological differences. 

 Its vesicles in the rabbit are occupied by closely crowded naked cells, 

 consisting of soft protoplasm. The organ in other animals as, for 

 instance, the dog (fig. 443), the cat, and in a minor degree, the sheep 

 departing from this form, have all the characters of a mucous gland. 

 Here the greater part of the vesicle is filled with large, clear, non-granular 

 cells, with a nucleus which is usually situated near the circumference (). 

 Besides these, we may see in the greater number of vesicles, close to the 

 border of the latter, a peculiar element usually of semicircular form, and 

 either single or double, the "crescent" of Gianuzzi (c). At first this appears 

 to be a granular mass of protoplasm with imbedded nuclei, but after being 

 subjected to a particular kind of treatment, it may be recognised to be a 

 collection of small highly compressed cells. Other saccules contain 

 protoplasm cells alone (b). These crescents reach the highest stage of 

 development in the submaxillary of the cat. 



The first of these elements we shall give them the name of mucous 

 veils present, after maceration, the most remarkable irregularity of 



outline. They may, however, 

 discharge their mucous con- 

 tents, as we shall see later on, 

 and then present protoplasm 



only- 

 Intermediate forms teach us 

 that these mucous cells are not 

 specifically different from those 

 of the crescent, or border cells, 

 but only so on account of their 

 having become altered and un- 

 dergone mucous metamorphosis. 

 In newly born animals they 

 are not yet to be found. The 

 submaxillary glands of man, like- 

 wise (specific gravity of 1*041, 

 accord in g to Krause and Fisch er), 

 contain the same mucous cells, 

 which require, however, closer 

 investigation. 



For a long time it was main- 

 tained that the submaxillary 

 pland possessed, most unquestionably, a structureless membrana propria. 

 More recent investigations, however, have shown that the boundary 

 layer is only formed of greatly flattened cells of stellate figure, which 

 probably belong to the connective- tissue group (Heidenhain, Koclliker), 

 194. 



i(?. 443. Submaxillary gland from the dog. a, mu- 

 cous cells; 6, protoplasm cells; c, "crescent" of 

 Qicmuzzi; d, transverse section of an excretory duct 

 with its special columnar epithelium. 



