SUBSTANCES SECRETED IN SALIVA. 503 



strong acids, the spheres and clumps gradually disappear. In strong solutions 

 of neutral salts (e.g. 20 per cent, sodium chloride), they may be kept for months 

 at any rate. Strong alcohol and mercuric chloride cause them to shrink and 

 make them* irregularly granular. Flemming's fluid turns many of them into 

 vacuolated spheres) with sharp outline and a few distinct small granules. No 

 mucous cells are seen in saliva after treatment with any of these reagents. 



In the submaxillary saliva of the cat, vacuolar and pale spheres are found, 

 but not the larger clumps. 



Microscopical constituents in saliva have been described by Eckhard, 

 Kiihne, and Heidenhain. The account I have given above differs in several 

 points from theirs. 



The most obvious view to take of these microscopical constituents 

 of saliva is, I think, that some of the mucous granules are turned bodily 

 out of the alveolar cells, 1 the fluid passing through the cells being 

 insufficient to dissolve them; and that by swelling up or massing 

 together they make the various forms of spheres and clumps which are 

 seen. But although the mucous granules behave with some reagents 

 very much as do the small spheres of saliva, and have in some states 

 very much the same appearance, their behaviour with acetic acid is 

 strikingly different. The mucous granules, on treatment with dilute 

 acetic acid, swell up and burst like bubbles ; 2 the spheres in saliva, as we 

 have seen, become refractive and obvious. Although it is possible that 

 this difference may depend on differences in the surrounding fluids, it is 

 sufficient to prevent more than a provisional acceptance of the view 

 that the spheres of saliva are simply undissolved mucous granules. 



SUBSTANCES WHICH ARE on WHICH MAY BE SECRETED IN SALIVA. S 



In saliva obtained from mucous glands, the chief organic constituent 

 is naturally mucin. Little is known with certainty of the varieties of 

 mucin which exist. In mucous saliva, whilst most of the mucin is 

 precipitated by acetic acid as a stringy lump, there is not infrequently 

 a portion which is precipitated in fine particles, these making the fluid 

 cloudy. A small quantity of proteid is also present, probably belonging 

 to the class of globulins. 



In saliva obtained from albuminous glands the proteid constituents 

 are globulin (or a body allied to globulin), alkali albuminate, and a 

 small amount of serum albumin. 4 



In typical mucous saliva, diastatic ferment is either absent, or 

 present in mere traces ; in saliva from albuminous glands, the amount 

 of diastatic ferment is variable and independent of the percentage of 

 proteid, but in the saliva of any one gland the diastatic action increases 

 with the percentage of proteid present. 



The salts are, so far as is known, the same in mucous and in 

 albuminous saliva, although their percentage amount varies considerably 

 in the saliva obtained from different glands. The bases found are 

 sodium, potassium, calcium, and magnesium ; the acids are hydrochloric 

 acid, carbonic acid, phosphoric acid, and sulphuric acid. Sodium 

 chloride is by far the largest constituent ; after this comes usually 



1 Langley, Proc. Eoy. Soc. London, 1886, vol. xi. p. 202. 



2 Langley, Journ. PhysioL, Cambridge and London, 1889, vol. x. p. 433. 



3 See also article on " Composition of Saliva," p. 342. 



4 Kiihne, " Lehrbuch. d. Physiol.," 1866. 



