

THE SECRETORY ACTIVITY OF THE SALIVARY GLANDS. 259 



THE SECRETORY ACTIVITY OF THE SALIVARY GLANDS. 



If the submaxillary gland of a dog is excited to active secretion by 

 stimulation of its nerves, the mucous cells are after a while no longer seen 

 but in their stead only smaller protoplasmic cells, devoid of mucus, within 

 the acini. The mucous cells have discharged their mucus into the secre- 

 tion of the gland, while their shrunken, dark-granular protoplasmic cell- 

 bodies remain (Fig. 94, C). These are capable, after a certain period 

 of rest, of producing new mucus. 



In regard to the crescents Stohr believes that they are produced mechanically 

 by inequality in the secretory phases in adjacent acinus-cells. The cells reduced 

 in size after having discharged their mucus are pressed to the wall by other cells 

 filled with mucus and therefore much swollen, and thus the flattened composite 

 marginal cells are formed. Recently R. Krause and others, differing from this 

 state that the composite marginal cells secrete only serum and have no relation 

 with the mucous cells. 



In the parotid gland of the rabbit, after secretion induced by stimula- 

 tion of the sympathetic nerve, the gland-cells assume a more shrunken 

 appearance, and their contents become more granular and more readily 

 stained. The nuclei appear rounder and exhibit a nucleolus (Fig. 95). 



Ranvier observed in the secretion of the albuminous glands (submaxillary 

 gland in the rat) that, after stimulation, many motile vacuoles were formed in the 

 gland-cells. The water of the secretion is formed in the vacuoles, and in its 

 excretion, carries with it the soluble ferment of the cells. A similar phenomenon 

 occurs within mucous cells and also in goblet-cells. Morphological changes occur 

 also in the cells of the salivary tubules. 



THE NERVES OF THE SALIVARY GLANDS. 



All the salivary glands derive their nerve-supply from two sources, namely 

 from the sympathetic nerve and from a cranial nerve. The nerve-fibers, chiefly 

 medullated, in part also non-medullated, pass in at the hilum and form a plexus 

 rich in ganglion-cells between the lobules of the gland. 



The sympathetic nerve sends branches (a) to the submaxillary and sublingual 

 glands, derived from the plexus surrounding the external maxillary artery (Fig. 

 243) ; (b) filaments pass to the parotid gland from the sympathetic plexus, which, 

 piercing the parotid, surrounds the external carotid artery. 



Of the cranial nerves, (a) the submaxillary and sublingual glands are supplied 

 by filaments from the chorda tympani branch of the facial nerve, (b) To the 

 parotid gland fibers pass from the glosso-pharyngeal nerve in the dog, especially 

 from its tympanic branch, which sends fibers through the tympanic plexus to the 

 lesser superficial petrosal nerve. Together with the latter the former pass down- 

 ward over the anterior surface of the petrous portion of the temporal bone, then 

 through the sphenoidal fissure to the otic ganglion. With the latter they con- 

 tinue through communicating branches to the auriculo-temporal nerve (from the 

 third division of the trigeminal nerve) , which, covered by the parotid gland, on 

 its way to the temple, sends the fibers to the gland. 



The submaxillary ganglion, which gives off fibers to the submaxillary and 

 sublingual glands, derives its roots from the tympanico-lingual plexus, as well as 

 from the sympathetic plexus about the external maxillary artery. 



With regard to the terminal distribution of the nerves to the salivary glands, 

 two varieties are to be distinguished: (i) the vasomotor nerves, which give branches 

 to the muscular walls of the blood-vessels, and (2) the true glandular nerves. 



According to Arnstein the latter form a surrounding network outside of the 

 gland-tubules. From this plexus fine filaments pierce the membrana propria and 

 terminate on the surface of the secreting cells with a peculiar end-apparatus: 

 namely, branched twigs possessing tiny bulbs or mulberry-shaped masses. The 

 same condition exists in the sebaceous, sudoriferous, and mammary glands and 

 in the pancreas. 



