1886.] Structure of Mucous Salivary Glands. 



363 



there are 8 to 12 granules. After a time the outlines of the granules 

 become indistinct ; this takes place much sooner in alkaline than in 

 neutral salt solution. 



The reactions of the granules are best observed by irrigating pieces 

 of gland which have been teased out in neutral salt solution. On 

 irrigating with dilute alkalis, dilute mineral acids, or with water, the 

 granules disappear as if they were bubbles bursting. It is difficult, 

 however, to be certain that they are completely dissolved; after treat- 

 ment with dilute mineral acids, and still more frequently after treat- 

 ment with water, pale, very slightly refractive masses are seen, appa- 

 rently consisting of swollen and altered granules.. On irrigating 

 with osmic acid the granules swell up considerably, and become less 

 refractive. On irrigating with alcohol or with acetic acid they 

 remain, but are somewhat shrunken. 



The hyaline substance of the cells swells up and in part dissolves in 

 3 per cent, sodium carbonate. The solution forms a viscid fluid ; on 

 irrigating with acetic acid or with alcohol a membranous precipitate 

 of mucin takes place. Since the granules are not, for a time at any 

 rate, dissolved by sodium carbonat-e, it follows that the hyaline sub- 

 stance gives rise to mucin. The granules also give rise to mucin ; in 

 most of their reactions they resemble mucin ; on solution they form 

 a viscid fluid ; further, when a gland is hardened in alcohol, and a 

 section mounted in Canada balsam or in glycerine, the granules in the 

 hyaline substance are usually indistinguishable, both together form 

 the clear mucigen portion of the cells. 



During secretion both the hyaline substance and the granules are 

 turned out of the cells ; after prolonged secretion the cells consist of 

 an outer zone, chiefly of freshly formed substance, and of an inner 

 zone of network, hyaline substance, and granules, as in the resting 

 state. When the saliva has a high percentage of solids, both the hya- 

 line substance and the granules can be seen in it ; such saliva is 

 obtained from the submaxillary gland of the dog by stimulating the 

 sympathetic, and often by strong stimulation of the chorda tympani. 

 The hyaline substance is more soluble than are the granules, and is 

 thus less commonly seen ; it is partly dissolved, partly swollen up into 

 a continuous mass ; the less swollen parts appear as strings or blebs. 

 The granules in saliva vary greatly in appearance ; they may be very 

 slightly swollen, and have fairly sharp outlines ; or they may be more 

 swollen and run together, forming pale masses of various size ; occa- 

 sionally in more dilute saliva they are just visible as pale spheres ; 

 these are probably the spheres mentioned by Heidenhain,* as seen 

 by him in the submaxillary saliva of the dog after combined stimula- 

 tion of the chorda tympani and sympathetic nerves. 



* " Studien des Physiol. Institute zu Breslau," p. 46, 1868. 



