132 



Blood Flow and Secretion 



these experiments it was concluded that the dilatation following 

 chorda stimulation or injection of acetylcholine is caused by some 

 fairly stable agent, which is normally eliminated by the lymph 

 after having produced its effect. In agreement with this latter con- 

 clusion it was found that the agent could not be demonstrated in 

 the venous blood. It was, however, shown to appear in the venous 

 effluent during chorda stimulation in a gland perfused with Locke's 

 solution. Such a perfusate was found to cause a vasodilatation when 



Time 

 30 sec 



Fig. 7.3. Records of venous outflow from submaxillary gland of a cat, of 

 secretion of saliva and arterial blood pressure. 



Effect of stimulation of the chorda-lingual nerve for 15 seconds (a), of arterial occlusion for 

 1 minute (b), and of chorda stimulation for the first 1 5 seconds of 1 minute arterial occlusion (<-) 

 (Hilton and Lewis, 19550). 



injected intra-arterially into a submaxillary gland with its normal 

 blood supply; likewise, it caused a fall in blood pressure on intra- 

 venous injection. An important further step in the analysis de- 

 pended on the observation that the venous perfusion sample, col- 

 lected during chorda stimulation, had no effect on smooth muscle 

 suspended in Tyrode solution but caused a contraction if previously 

 incubated with plasma. This is illustrated in Fig. 7.4. Further 

 experiments showed that the contraction obtained, and the vaso- 

 dilatation as well, is due to the polypeptide bradykinin or kallidin 

 of Rocha e Silva, Beraldo and Rosenfeld (1949) and Frey, Kraut 

 and Werle (1950). 



