4 88 THE SALIVARY GLANDS. 



1. Sympathetic stimulated for two and a half hours. The resting gland 

 had 25 per cent, of solids, the stimulated gland 23 '6 per cent. 



2. Sympathetic stimulated for five and a half hours. The resting gland 

 had 25 per cent, of solids, the stimulated gland 24*4 per cent. 



We may conclude, then, that during secretion the gland cells 

 decrease in weight, and therefore that they increase in weight during 

 rest. The increase in rest might be due, as we have said, to a taking up 

 of oxygen. But the observations of Pawlow, 1 if they are well founded, 

 show that, whether an increase in weight due to oxygen combinations 

 occurs or not, there is during rest a not inconsiderable increase in the 

 nitrogen of the glands, and this can hardly be due to anything else than 

 an absorption of proteids. Pawlow estimated by Kjeldahl's method the 

 amount of nitrogen in the resting submaxillary gland of the dog on the 

 one hand, and in the stimulated gland and in the saliva secreted by it 

 on the other hand. He obtained saliva by stimulating the central end of 

 the sciatic for one and a half to five hours. In ten (right) stimulated 

 glands he found 1*872 grms. nitrogen. In the ten (left) non-stimulated 

 glands he found 2*18 grms. of nitrogen. Assuming, then, that the glands 

 had the same amount of nitrogen to start with, the stimulated 

 glands had lost during secretion about \ of their nitrogen -holding 

 substance. In the saliva secreted he found 0416 grms. of nitrogen, 

 so that presumably the glands had taken up during secretion about 

 01 grm. of nitrogen ; this is about ^r f the total amount. The 

 numerical results are not such as we should expect from the micro- 

 scopical appearances of the gland cells, and it is desirable that the 

 experiments should be repeated. 



The general characters of the cells of the lobular ducts suggest that 

 they are not simply the lining cells of a conducting tube, but are rather 

 active constituents of the gland, concerned either with adding to the 

 saliva as it passes by them, or with subtracting from it. There is not, 

 however, any clear evidence on the matter. It is true that when a con- 

 siderable amount of methylene-blue is injected into the blood, and the 

 glands are excited to secrete, small deep blue particles may be found in 

 the duct cells as in the alveolar cells, but methylene-blue is so readily 

 taken up by many tissues that little trust can be placed on this as show- 

 ing a secretory function. The cells of the lobular ducts contain small 

 granules in their outer portion, 2 and, according to Mislawsky and 

 Smirnow, 3 these granules decrease during secretion, but it does not 

 appear to me certain that the changes described by these authors are not 

 due to conditions other than secretory activity. Merkel 4 observed that 

 the cells with striated epithelium, i.e. most of the lobular duct cells of 

 the submaxillary and parotid glands, stained a deep brown when treated 

 with pyrogallic acid in the presence of oxygen. He considered that the 

 stain was due to the presence of calcium salts in the cells. This 

 naturally suggested that the lobular ducts with striated epithelium might 

 secrete calcium salts. But Werther 5 has shown that the percentage of 

 calcium salts in the sublingual saliva of the dog is rather greater than in 



1 Centralbl.f. PhysioL, Leipzig u. Wien, 1888, S. 137. 



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

 granules of the duct cells swell up and become indistinct, the substance between them takes 

 on the characteristic striated appearance seen in hardened specimens. 



3 Arch. f. Anat. u. PhysioL, Leipzig, 1896, Physiol. Abth., S. 93. 



4 "Die Speichelrohren," Leipzig, 1883. 



5 Arch.f. d. yes. PhysioL, Bonn, 1886, Bd. xxxviii. S. 293. 



