284 HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS. 



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

 found that, during rest, the substance of the cells of the parotid is per- 

 vaded by fine granules, which are so numerous as to obscure the nucleus, 

 while the outlines of the cells are indistinct. No lumen is visible in 

 the acini during activity, the granules disappear from the outer zone of 

 the cells, the cells themselves becoming more distinct and smaller. After 



Fig. 118. Fig. 119. 



Sections of a "serous " gland the parotid of a rabbit, Fig. 118, at rest ; Fig. 119, 

 after stimulation of the cervical sympathetic. 



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 round 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 dis- 

 appearance taking place from without inwards. Similar changes occur 

 in the cells of the pancreas.] 



[Mucous Glands. 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. 116, B, c), surrounded with a small amount of 

 protoplasm, and placed near the basement membrane. The clear sub- 

 stance does not stain with carmine, and consists of mucigen 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, refractive, 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 (Fig. 116, C), devoid of mucin. These cells 



