46-4 MANUAL OF HISTOLOGY. 



and Schmidt have estimated it at 1500 grammes in man, but also at a 

 lower figure. 



Its action and use are, in the first place, the same as water ; further, as 

 a slimy fluid it lubricates the various matters taken into the mouth, 

 causing them to pass the more easily into the oesophagus; and then again 

 its action on starch (C 6 H 10 5 ) is chemical, transforming the latter into 

 dextrine (C 6 H 10 5 ) and grape sugar (C 6 H 12 6 ). It is the ptyalin alone 

 which here acts as a ferment. 



Let us now turn to each of the secretions in succession of which the 

 saliva is composed, taking first the mucus of the mouth. The amount of 

 this is inconsiderable, if we are to judge from experiments on animals. 

 It was found by Bidder and Schmidt to contain water to the amount of 

 99 per cent. In the mucus of the mouth we find, likewise, an abundance 

 of form elements, flattened epithelium cells, and salivary corpuscles. 



Of all these secretions, that with which we are best acquainted is the 

 saliva obtained from the submaxillary gland of the dog. As was shown 

 many years ago by Ludivig, the secretion of this fluid is presided over by 

 the nervous system. From a whole series of experimental studies, partly 

 undertaken by Ludwig and his pupils, partly by Koelliker and Muller, 

 Czermak, Bernard, Eckhard, Adrian, and Heidenhain, we have become 

 acquainted with, the following points of interest. The submaxillary 

 gland receives, first of all, branches from the facial nerve, mixed with a 

 small contingent of the trigeminus : this is the continuation of the chorda 

 tympani. In the second place, a number of filaments of the sympathetic 

 enter the organ with the arteries. Finally, it receives nervous offsets 

 from the submaxillary ganglion, which run with the chorda through the 

 organ, and are excited by reflex action from the tongue through the 

 lingualis. 



Irritation of the chorda tympani gives rise to the secretion of a large 

 quantity of a strongly alkaline and non-viscid fluid, whose proportion of 

 water is about 99 per cent. Together with this the gland becomes filled 

 with a larger quantity of blood than usual ; the pressure in the veins is 

 increased, and the whole mass of the blood, leaving the organ, presents a 

 bright red colour (Bernard), while the temperature of the latter rises 

 about 1 C. (Ludwig and Spiess). That this secretion is independent of 

 the increased influx of blood is clear from the fact, that after interruption 

 of the flow through the carotid, as well as in a head severed from the 

 body, it may be induced by stimulation of these nerves. 



Stimulation of. the sympathetic salivary nerves, on the other hand, has 

 quite a different effect (Czermak, Eckhard). Here the circulation is con- 

 siderably retarded, and the venous blood leaving the organ is of a dark 

 red colour. A small quantity only of a very viscid, cloudy, and strongly 

 alkaline secretion issues from the excretory duct, containing solid con- 

 stituents in the proportion of from 1'6 to 2 '8 per cent. 



In the saliva given off after stimulation of the chorda, mucin has been 

 found with various albuminous substances. After irritation of the sym- 

 pathetic it is also very rich in mucin. As far as we know, neither of these 

 secretions of the submaxillary gland have any action on the food, with 

 the exception of a slight power of producing sugar manifested by the 

 sympathetic saliva of the dog. 



The form elements appearing in these two kinds of saliva of the sub- 

 maxillary are of great interest. Many years ago numerous pellets of 

 colloid matter were noticed by Eckhard in the sympathetic secretion of 



