Changes in Sensitivity to Chemical Stimuli 1 07 



huber and Evans, 1954) but observations have also been made on 

 the parotid gland (Stromblad, 19556; Nordenfelt and Ohlin, 1957) 

 and the sublingual gland (Emmelin, 1953*2). 



These various investigations show that supersensitivity can be 

 produced by parasympathetic and by sympathetic denervation, 

 that the supersensitivity of one type resembles that of the other 

 but is usually much more pronounced in the former, and that one 

 supersensitivity can be superimposed upon the other. 



Fig. 6.1. Supersensitivity to adrenaline after section of the chorda tympani in a 

 cat under chloralose anaesthesia. 



From above : Drops of saliva from the right submaxillary gland. The right chorda cut two weeks 

 previously. Drops from the left, innervated gland. Intravenous injection of adrenaline in doses of 

 1-20 //g/kg. Times in minutes (Emmelin, unpublished). 



Fig. 6.1 shows the effect of different doses of adrenaline, in- 

 jected intravenously, on the submaxillary gland two weeks after 

 section of the chorda, and on the contralateral intact gland. Many 

 of the characteristics of the hypersensitivity are shown in this 

 figure. It can be seen that denervation lowers the threshold. A 

 moderate dose of adrenaline causes a bigger response, because the 

 rate of secretion is increased and the gland secretes for a longer 

 period. When a big dose is given, causing secretion at a maximal 

 rate, however, the flow is not quicker from the denervated than 

 from the innervated gland; it may be somewhat slower, because 

 of the atrophy of the decentralized gland. 



Supersensitivity develops gradually; it can first be detected 

 after two or three days, and reaches its maximum after two or 



