328 COLLOIDS IN BIOLOGY AND MEDICINE 



The Saliva. 



Under normal circumstances, 700 to 1000 c.c. of saliva are secreted 

 daily. The amount of salivary secretion is largely influenced by 

 the amount of water contained in the body. If large amounts of 

 water are taken, the salivary secretion is plentiful, whereas, with 

 diarrhea, profuse sweating and fever, it diminishes greatly (dry 

 mouth). 



Of all the secretions, the saliva has on the average the lowest 

 osmotic pressure; its freezing-point depression is from 0.11 to 0.27 in 

 man, in contrast to blood with from 0.58 to 0.60. If the excretion of 

 saliva increases, there is an increase in the crystalloids contained and 

 to such an extent that when the secretion is greatest it almost reaches 

 that of blood plasma; it then contains 0.58 per cent NaCl. The 

 fact that with increased salivation the carbonates are proportionately 

 increased in the saliva, strongly supports in my opinion the role of 

 ultrafiltration of the blood plasma in the secretion of the saliva. If 

 the NaCl content of the blood is increased, that of the saliva also 

 increases, and conversely (J. NOVY, J. N. LANGLEY and FLETCHER). 

 If potassium iodid or lithium citrate are introduced into the cir- 

 culation (J. N. LANGLEY and FLETCHER), iodin or lithium may be 

 demonstrated in the saliva immediately; whereas, after introducing 

 grape sugar and potassium ferrocyanid they do not appear in the 

 saliva at all or only after a long time. All these facts support the 

 view that the chief process is an ultrafiltration. The last-mentioned 

 experiments, especially, show that potassium iodid and lithium citrate, 

 which diffuse rapidly and open paths, appear in the saliva promptly, 

 whereas grape sugar and potassium ferrocyanid, as a result of their 

 slowness in diffusion, penetrate the filter membrane slowly, so that 

 meanwhile they may be excreted in other ways. For the two remain- 

 ing elements in the function of the salivary glands, the change in the 

 composition of the ultrafiltrate and the addition of the colloid con- 

 stituents, we have as yet no experimental data. 



The Bronchial Glands. 1 



An analysis of the individual functions of the secretion of the 

 bronchial mucous membrane has proved hitherto entirely impossible. 

 It is an indication of ultrafiltration that with an increase in the 



1 MARTIN H. FISHER with justice questions why the secretion of superfluous 

 water commences in the kidneys instead of in the lungs, since by the change of 

 the venous blood rich in carbonic acid into arterial blood, water is actually 

 liberated. He thinks that water is not secreted in the lungs because of the im- 

 permeability of the membrane, or because there is insufficient time. 



