XXIIL] THE! PANCREAS. 265 



pilocarpin. It is then removed from the body and hardened in one of the 

 ways stated on p. 258. It is essential that the active and non-active glands 

 be hardened in the same way, so as to show that such differences as exist are 

 not due to the method of hardening. 



(H) Observe that the mucous cells are not so clear as in the passive gland, 

 but are more granular and smaller, while in stained sections part of their cell- 

 substance is stained by the pigments, and thus there is less difference between 

 the demilunes and the mucous cells. The nuclei become more spheroidal. All 

 the acini in the section are not necessarily in the same phase of activity, so 

 that the appearances in any two acini may not be identical. 



13. Isolated Mucous and Demilune Cells. (i.) Place fragments of a fresh 

 dog's sub-maxillary gland in 5 per cent, ammonium chromate (4-6 days). 

 Tease a small piece in the same fluid. Note the isolated mucous cells, each 

 with its fibrillar network, spherical nucleus embedded in protoplasm, and 

 what was the attached end of the cell prolonged into a process. 



(ii. ) The cells, membranes, &c., are readily isolated in 33 per cent, caustic 

 potash. 



14. Mucous Granules. The mucous granules are readily seen by "fixing" 

 a small piece of the gland with the vapour of osmic acid (Langley}.* 



15. Salivary Glands of Cockroach. It is better to use the species Peri- 

 plancta amcricana. Kill the animal with chloroform. Pin it out on its back 

 on a cork plate and make the dissection in normal saline. On cutting open 

 the thorax longitudinally one sees the intestinal tract, and on each side of 

 this, lying on the wall of the latter, are the flattened salivary glands. They 

 can readily be removed. They may be examined fresh, or stained in picro- 

 carmine, or exposed to the vapour of osmic acid, and mounted in glycerine. 

 They show well the general arrangement of ducts and lobules. Each duct is 

 lined by a spiral chitinous fibre like the tracheae. 



16. Terminations of Nerves in Serous Glands. The rapid hardening 

 method of Golgi (Lesson XXX.) as directed for the pancreas has been used by 

 Fusari and Panasci ' 2 for the nerve terminations in the serous glands of the 

 tongue of the rat, rabbit, and cat. The terminal fibrils form an epilemmal 

 plexus, i.e. , outside the basement membrane, and other fibrils pass between the 

 gland cells, i.e., are hypolemmal. Fusari's paper is accompanied by a plate. 



17. Gland-Ducts. Sometimes on using Golgi's method one gets the lumen 

 of the ducts black. If this happens, then an excellent view is obtained of 

 their course and connections. 



18. Fresh Pancreas. In the rat and rabbit the pancreas is spread out in 

 lobules in the mesentery, and if a piece of this containing a thin part of the 

 pancreas be stretched on a ring of cork the granules can be seen in the fresh 

 alvi-olar cells. Osmic acid does not alter the granules much, but alcohol does. 



19. Changes in Pancreas Cells may be seen in frogs one fed say three or 

 four days previously, and the other a few hours before it is required. 



20. Rodded Structure in Cells. Macerate a small piece of fresh pancreas in 

 5 per cent, ammonium chromate for 2-3 days ; tease and examine in the same 

 fluid. The outer part of some of the cells will be found to be " rodded." 



21. Outer and Inner Zones of Pancreas Cells. (a.) Use the pancreas of a 

 starving animal. To stain the outer zone, use ammoniacal or borax-carmine, 

 and for the granules of the inner zone stain a section (fixed on a slide) with 

 metliyl-green-fuchsin-S solution made by mixing methyl -green (i per cent.) 

 60 cc. with fuchsin-S solution (i per cent. ) 20 cc. Stain lor 10 minutes. Wash 

 quickly in water. Mount in balsam. The granules are red, and the outer 

 zone clear. [Fuchsin-S is acid-fuchsin. ] For preparations from Flemming's 



1 Journal of PJt ?/.s?Ww/?/, vol. x. p. 433. 



2 Arcliiv. ital. dc J! /'<>/., xiv. p. 240, 1891. 

 24 



