2 CHEMICAL PHYSIOLOGY. 



tubes have to be carefully introduced into the respective 

 ducts, which is a matter of some difficulty. For this 

 reason the chemical composition of the secretions of 

 the separate glands is very imperfectly known. Ex- 

 periments upon animals have shown that these glands 

 can give four different kinds of secretion, according to 

 the nerves which are irritated for the purpose. One 

 nerve, a branch of the facial, and a continuation of the 

 chord of the tympanum, on irritation causes a clear, 

 slightly ropy secretion from the submaxillary glands. 



sauTa dal ^is "chordal" saliva contains about 4 per cent, of 

 solid matters, of which 1*5 are globuline, mucine, and 

 coagulable albumen ; 2*5 per cent, are mineral, mainly 

 alkaline chlorides and lime-salts ; of these latter the 

 carbonate, dissolved in excess of carbonic acid, fre- 

 quently decomposes in the mouth, and deposits crusts 

 of lime carbonate upon the teeth, which are popu- 



ia7va athetic l ar ty called tartar. On irritation of the sympathetic 

 nerve the submaxillary glands secrete an opaque very 

 tough saliva. This contains from 15 to 28 per mille 

 of solids, amongst which is mucine, and granules or 

 roundish lumps of an albuminous matter, and much 



S! nic f ree alkali. The third kind of saliva is that which 

 flows when the submaxillary ganglion is made the 

 centre of a reflex action which works by way of the 

 lingual nerve. This is the only secretory act without 

 the intervention of cerebro-spinal influence that is 

 known at present. The fourth kind of saliva is the 



paralytic " paralytic " or thin watery fluid which is secreted under 

 the influence of nervous paralysis, caused either by 

 degeneration, or poisoning, or wounds which separate 



