XX] SALIVARY GLANDS 161 



9. Sections of dog's orbital gland hardened in osmic acid 

 vapour, given out in paraffin. 



(a) Stain some sections on a cover-slip with alcoholic 

 methylene blue. Observe the deeply stained mucous granules 

 stretching throughout the cells. The protoplasmic cell substance 

 is stained greenish. 



(6) Place a section in xylol to dissolve the paraffin, transfer 

 to absolute alcohol, mount in 95 p.c. alcohol. Observe the 

 brownish mucin granules. Irrigate with 50 p.c. alcohol, watching 

 the cells carefully. 



The granules will be seen to swell up till their outlines are 

 lost ; the cells swell, their outlines become rounded ; an intra- 

 cellular network becomes visible; thus the general appearance 

 of the hardened gland of 6 is obtained. Transfer to absolute 

 alcohol and the original appearance will return. (If the tissue has 

 been too short a time in osmic acid vapour the granules as they 

 swell may stick together ; in this case absolute alcohol brings back 

 the original appearance imperfectly or not at all.) 



DEMONSTRATIONS. 



1. Transverse section of the hilus of the sub- 

 maxillary gland of a cat or dog. Note ; the branching 

 duct with large lumen and one or two layers of cubical 

 or flattened epithelium cells ; close to the duct groups 

 of nerve-cells forming part of the sub-maxillary gan- 

 glion; the gland artery, and probably a vein. 



2. Section of dog's active sub-maxillary gland 

 (osmic acid vapour ; methylene blue) to show the inner 

 granular and outer protoplasmic zones. Note the 

 mucous granules, stained deep blue, confined to the 

 inner portions of the cells. 



L. 11 



