5™ 
THE SALIVAR Y GLANDS. 
There are no experiments which show definitely what is the effect on 
the percentage composition of 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 1 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. 
Eelation 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. cit. 
- Arch.f. Anat. u. Physiol., Leipzig, 1888, Physiol. Abth., S. 403. 
3 Arch.f. d. ges. Physiol., Bonn, 1874, Bd. ix. S. 346. 
4 Hermann's "Handbuch," 1880, Bd. i. Th. 1, S. 73. 
