References 101 



various observations indicate that there is a fundamental difference 

 beween the continuous sublingual secretion and a secretion evoked 

 by extrinsic agents. 



Spontaneous secretion is certainly not due to a high permeability 

 of the gland cells resulting merely in filtration of fluid. Several 

 arguments can be adduced against such an assumption. The sub- 

 lingual gland of the cat is able to secrete against a pressure of 

 about 1 5 cm of water ; this is true even if the gland is isolated in 

 Tyrode solution. The flow occurs at a fairly constant rate against 

 different counter-pressures in the salivary ducts. Similarly, great 

 variations in arterial blood pressure affect the rate of flow very little 

 and a perceptible flow has been found as late as 45 minutes after 

 death. The very viscous saliva even from an isolated gland re- 

 sembles very little a simple filtrate of plasma. The finding that 

 cyanide stops the flow indicates that metabolic processes are neces- 

 sary for the continuous secretion. This effect is obtained within 

 a few minutes in a perfused gland. It can be demonstrated on the 

 isolated gland, also, as shown in Fig. 5.1. 



REFERENCES 



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Nierensecretion. Beitr. Anat. Physiol., 4, 89-107. 

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by the parotid gland of the sheep. J. Physiol, 131, 13-31- 

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 — (1893). Noch einmal die Parotis des Schafes. Centralblatt f. Physiol., 



7, 365-368. 

 edkins, j. s. (1906). The chemical mechanism of gastric secretion. J. 



Physiol., 34, 133-144- 

 ellenberger, w. and v. hofmeister (1887). Beitrag zur Lehre von der 



Speichelsecretion. Arch. Anat. Physiol., Physiol. Abt., Suppl.-Band 



11, 138-147. . . ,. - , A . . j 



emmelin, N. (1953). On spontaneous secretion ot saliva. Acta physwl. 



scand., 30, Suppl. in, 34-58. 



emmelin, N. and A. muren (1950)- Acetylcholine release at parasym- 

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florey, h. (1930). The secretion of mucus by the colon. Brit. J. exp. 

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