260 



PRACTICAL HISTOLOGY 



[XXIIL 



FlG. 249. Small Lobule of a Sub-Maxillary Gland, Dog. 

 L. Lobule ; D. Duct. Osmic acid. 



between the lobules. Some of the acini appear to be crowded with 

 cells inside the basement membrane. The gland-ducts have a 

 distinct lumen. 



(c.) (H) Although numerous acini are visible, only those that 



have been cut across 

 so as to show the 

 lumen are satisfactory; 

 the others appear 

 merely to be filled 

 with cells, and vary 

 much in size, accord- 

 ing to the plane of 

 section through the 

 alveolus. Each aci- 

 nus has a clear, trans- 

 parent basement mem- 

 brane, and inside, and 

 on it, is arranged the 

 secretory epithelium. 

 (d.) The mucous cells form a single layer, and are large, clear, 

 cubical cells. Each has a nucleus which is usually flattened and 

 placed near the attached end of the cell. In borax-carmine pre- 

 parations, the nucleus, surrounded by granular protoplasm, is stained 

 red, while the rest of the cell appears clear, and traversed, it may 



be, by fine threads or 

 fibrils. In reality, the 

 coil-substance consists of 

 a network containing a 

 clear substance muci- 

 gen. 



(c.) The demilunes lie 

 singly next the basement 

 membranes. Two or 

 three may be seen in the 

 section of each alveolus 

 as more granular deeply- 

 stained bodies, sometimes 

 with two nuclei. As 

 their name indicates, 

 they are somewhat half- 

 moon shaped, but they 

 send processes between the mucous cells. As they are deeply 

 stained by pigments and also darkened by osmic acid, their shape 

 and distribution are readily recognised. 



(/.) The lumen of each acinus is a small more or less regular 



FlG. 250. Sub-Maxillary Gland, Dog, showing Duct 

 Communicating with an Alveolus by a Narrow 

 Ductule. The alveoli with mucous cells and dense 

 demilunes. Osmic acid and hasmatoxylin, x 300. 



