286 THE ORGANS 



lying upon the main excretory duct and some of its larger branches; 

 those sending axones to the sublingual being situated in a small gang- 

 lion — the sublingual — lying in the triangular area bounded by the 

 chorda tympani, the lingual nerve, and Wharton's duct; those sup- 

 plying the parotid probably being in the otic ganglion. Axones 

 from these cells enter the glands with the excretory duct and follow 

 its branchings to the terminal tubules, where they form plexuses 

 beneath the epithelium. From these, terminals pass to the secreting 

 cells. It is probable that the salivary glands also receive sympathetic 

 fibres from cells of the superior cervical ganglia. 



TECHNIC 



(i) The salivary glands should be fixed in Flemming's fluid (technic 8, p. 8), 

 or in formalin-Miiller's fluid (technic 6, p. 7). Sections are cut as thin as possi- 

 ble, stained with haematoxylin-eosin (technic i, p. 20), and mounted in balsam. 



(2) For the study of the secretory activities of the gland cells, glands from a 

 fasting animal should first be examined and then compared with those of a gland 

 the secretion of which has been stimulated by the subcutaneous injection of pUo- 

 carpine. Fix in Flemming's or in Zenker's fluid (technic 10, p. 8). Examine 

 some sections unstained and mounted in glycerin, others stained with haema- 

 toxylin-eosin and mounted in balsam. 



(3) The finer intercellular and intracellular secretory tubules are demon- 

 strated by Golgi's method. Small pieces of absolutely fresh gland are placed 

 for three days in osmium-bichromate solution (3-per-cent. potassium bichromate 

 solution, 4 volumes; i-per-cent. osmic acid, i volume), and then transferred with- 

 out washing to a 0.75-per-cent. aqueous solution of silver nitrate. Here they 

 remain for from two to four days, the solution being frequently changed. The 

 processes of dehydrating and embedding should be rapidly done, and sections 

 mounted in glycerin, or, after clearing in xylol, in hard balsam. 



Pancreas 



The pancreas is a compound tubular gland. While in general 

 similar to the salivary glands, it has a somewhat more complicated 

 structure. A connective-tissue capsule surrounds the gland and 

 gives off trabeculae which pass into the organ and divide it into lobules. 



In some of the lower animals, as for example the cat, these lobules 

 are well defined, being completely separated from one another by 

 connective tissue. In this respect they resemble the lobules of the 

 pig's liver. A number of these primary lobules are grouped together 

 and surrounded by connective tissue, which is considerably broader 

 and looser in structure than that separating the primary lobules. 

 These constitute a lobule group or secondary lobule. 



In the human pancreas the division into lobules and lobule groups 



^ 

 ^ 



