5 T o THE SALIVAR Y GLANDS. 



There are no experiments which show definitely what is the effect on 

 the percentage composition oj 5 saliva of a decrease of blood supply due 

 to simple constriction of the vessels. When the cranial nerve is 

 stimulated during compression of the carotid artery, the blood flowing 

 through the gland flows through dilated vessels. When the diminution 

 in blood supply is brought about by stimulating a vaso-constrictor 

 nerve, the blood flowing through the gland flows through constricted 

 vessels. It is probable that, in the former case, fluid passes more 

 readily through the vessel walls; hence, with the same amount of 

 organic substance secreted in the two cases, one saliva might have a 

 low and the other a high percentage of organic substance. 



Changes in the amount and character of the saliva l may, however, 

 be produced by variations in the character of the blood. The injection 

 of a considerable quantity of dilute salt solution, such as - 2 per cent., leads 

 to a considerable increase in the rate of secretion of saliva, whether this 

 is set up by stimulating the chorda tympani or by injecting small 

 quantities of pilocarpine. Up to a certain point the percentage of 

 salts increases in the normal manner ; beyond this the percentage ceases 

 to increase and may fall. An increase in rate may also be produced by in- 

 jecting into the blood 100 c.c. to 250 c.c. of stronger solution (as 2 per cent.) 

 of sodium chloride or sodium carbonate. Probably this amount leads to 

 the passage of water from the tissues, and so increases the volume of the 

 blood. The injection may cause an increase in the percentage of salts. 

 Injection of strong salt solution into the blood, in quantity sufficient to 

 increase the percentage of sodium chloride in the serum, was found by 

 Novi 2 to increase the percentage of the salt in submaxillary saliva; 

 though never up to that in the serum. When a certain amount of strong 

 salt solution (20 per cent.) is injected, the gland becomes cedematous, 

 and neither placing acids on the tongue (Novi), nor stimulating the 

 chorda tympani, nor injecting pilocarpine (Langley and Fletcher), will 

 cause a secretion. 



KELATION OF SECRETION TO THE FLOW OF LYMPH. 



We know very little with regard to the flow of lymph from the 

 glands in various conditions. The lymph vessels leave the submaxillary 

 gland at the hilus. If the lymph could be collected and analysed, it 

 would give information very much needed with regard to the secretory 

 activity. Heidenhain, 3 who has paid some attention to the subject, 

 appears only to have noticed whether oedema of the gland was produced 

 or not, but it is manifest that if the lymph vessels were large there 

 might be very great increase in the lymph flow without oedema. 



Heidenhain 4 considers that there is no increase in lymph flow from 

 the gland during stimulation of the chorda, either before or after giving 

 atropine. Supposing, then, that atropine does not act on the vessel wall, 

 so as to hinder the passage of fluid through it, it would follow that fluid 

 passes from the vessels in increasing amount, as an increasing amount 

 of saliva is secreted by the gland. In other words, it would follow that 

 there is in rest a certain slight constant formation of lymph, and that, 



1 Cf. Langley and Fletcher, op. tit. 



2 Arch.f. Anat. u. PhysioL, Leipzig, 1888, Physio! . Abth., S. 403. 

 s Arch.f. d. ges. PhysioL, Bonn, 1874, Bd. ix. S. 346. 



4 Hermann's "Handbueh," 1880, Bd. i. Th. 1, S. 73. 



