SECRETION PHYSIOLOGY. 305 



in mm. Chorda-lingual divided in each case. Cervical sympa- 

 thetic divided and stimulated by tetanic shocks, secondary coil 

 180-100 mm. The chorda was first stimulated intermittently 

 for an hour, so that the glands were secreting watery saliva. 



Cat. Dog. 



i ii iii i ii 



1st 10 seconds of sympathetic stimulation ... 10 .. 9 lo . . , 25 . . 17 



2d '• " " " " . . . 9 . . 5 . . 6 . . . 4 . . 2 

 3d" " " " " ...0..0..0...3..2 



4th " " " " " . . . o . . o . . o . . 2 . . I 



5th " " " " " . . . o , . o . . o . . . 2 . . 2 



oft' oft" oft' 



6th " " " " " , . . o . . o . . o . . . 8 . . I 



off" oft" 



By inspection of these figures, it is seen that on stimulation 

 the secretion comes suddenly, reaches its maximum rate of flow 

 in the first few seconds, and then quickly subsides. In the cat, 

 it abruptly ceases after 20 seconds. In the dog, probably owing 

 to the greater viscidity of the saliva and the resistance offered to 

 its passage by the fine gland-tubules, it persists slightly through- 

 out the stimulation. 



Heidenhain attributes the abrupt cessation of secretion, after 

 a few seconds, to the vaso-constrictor action of the nerve, in 

 consequence of which the secretory mechanism is, as it were, 

 suffocated.-^ That this explanation is incorrect may readily be 

 shown by cutting off the blood by compressing the gland's 

 artery, or by decapitation. In such cases, as the following ex- 

 periments show, a perfectly typical secretion may ensue on 

 stimulation of the sympathetic, ten or more minutes after liga- 

 turing the artery, or decapitation. 



Experiment Va. 



(A full account of this experiment is given on page 343.) 

 Large dog, which had received 3CC. i % morphine sulphate 

 subcutaneously. Ether given through tracheal tube. Sub- 

 maxillary dissected free, and remained attached only at the 

 hilus and by its veins. Chorda-lingual and sympathetic cut. 

 Canula connected with tube graduated in millimeters in Whar- 

 ton's duct. Gland's artery exposed by extirpation of the 

 digastric muscle. Tetanic shocks. Secondary coil at i 50. The 



