210 HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS. 



granules, and a small, irregular, red-stained, shrivelled nucleus devoid of a nucleolus. 

 The appearance of the nucleus suggests the idea of its being shrivelled by the 

 action of the hardening reagent (fig. 157.] 



[During activity, if the gland be caused to secrete by stimulating the sympa- 

 thetic, all parts of the cells undergo a change (figs. 157, 158). In preparations 

 hardened in alcohol (1) the cells diminish somewhat in size ; (2) the nuclei 

 are no longer irregular, but round, with a sharp contour and nucleoli; (3) the sub- 

 stance of the cell itself is turbid owing to the diminution of the clear substance, 

 and the increase of the granules, especially near the nuclei ; (4) at the same time, 

 the whole cell stains more deeply with carmine (Heidenhain).'] 



[On studying the changes which occur in a living serous gland, Langley found 

 that the substance of the cells of the parotid is pervaded by fine granules, which 



Fig. 157. Fig. 158. 



Sections of a "serous" gland. The parotid of a rabbit, fig. 157, at rest; fig. 158, after 

 stimulation of the cervical sympathetic. 



are so numerous as to obscure the nucleus, while the outlines of the cells are indis- 

 tinct. No lumen is visible in the acini during activity, the granules disappear 

 from the outer zone of the cells, the cells themselves becoming smaller and more 

 distinct. After prolonged secretion, the granules largely disappear from the cell- 

 substance except quite near the inner margin. The cells are smaller, their outlines 

 more distinct, their spherical nuclei apparent, and the lumen of the acini is wide 

 and distinct. Thus, it is evident that, during rest, granules are manufactured, 

 which disappear during the activity of the cells, the disappearance taking place 

 from without inwards. Similar changes occur in the cells of the pancreas.] 



[More complex changes occur in the mucous glands, such as the sub-maxillary 

 or orbital glands of the dog (Lavdovsky). The appearances vary according to the 

 intensity and duration of the secretory activity. The mucous cells at rest are large, 

 clear, and refractive, containing a flattened nucleus (fig. 155, C), surrounded with a 

 small amount of protoplasm, and placed near the basement membrane. The clear 

 substance does not stain with carmine, and consists of raucigen lying in the wide 

 spaces of an intracellular plexus of fibrils. After prolonged secretion, produced, 

 it may be, by strong and continued stimulation of the chorda, the mucous cells of 

 the sub-maxillary gland of the dog undergo a great change.] The distended, re- 

 fractive, and " mucous cells," which occur in the quiescent gland, and which do not 

 stain with carmine, do not appear after the gland has been in a state of activity. 

 Their place is taken by small dark protoplasmic cells devoid of mucin (fig. 155, C). 

 These cells readily stain with carmine, whilst their nucleus is scarcely, if at all, 

 coloured by the dye. The researches of R. Heidenhain (1868) have shed much 

 light on the secretory activity of the salivary glands. 



The change may be produced in two ways. Either it is due to the " mucous cells" during 

 secretion becoming broken up, so that they yield their mucin directly to the saliva ; in saliva rich 



