46 Innervation of the Glandular Elements 



In "the chorda tympani syndrome" (Young, 1956) unilateral 

 sweating occurs in the submental region during meals. i\fter a 

 previous accidental injury to the chorda, for instance during re- 

 moval of tuberculous cervical lymph glands, misdirected regenerat- 

 ing chorda fibres have innervated sweat glands and, when food is 

 taken, impulses meant for the salivary gland cells reach the sweat 

 glands instead. Since the sudomotor fibres are cholinergic (Dale 

 and Feldberg, 1934) the inference would again be that the pre- 

 ganglionic chorda fibres are cholinergic too. 



The average quantity of acetylcholine liberated at the pre- 

 ganglionic terminals for each volley in the chorda tympani was 

 found to be about 20 pg in the cat's submaxillary gland, perfused 

 with plasma containing eserine and curarine, when the nerve was 

 stimulated for two minutes at a frequency of 20 per sec (Emmelin 

 and Muren, 1950). For comparison it may be mentioned that this 

 figure is almost as high as that obtained under similar experimental 

 conditions in the superior cervical ganglion of the cat (Emmelin 

 and Macintosh, 1956). When the gland was perfused without 

 curarine, the average output of acetylcholine per volley was about 

 80 pg; the contribution of the preganglionic endings would thus be 

 about 20, that of the postganglionic endings about 60 pg. The ratio 

 of preganglionic axons to ganglion cells in the chorda is not known; 

 it is generally supposed to be low in the parasympathetic system, 

 of the order of 3 to 1 or 2 to 1 so that the quantity of acetylcholine 

 released per shock is probably of the same order at the pre- and 

 postganglionic ending. 



In order to be accepted as a mediator between the parasym- 

 pathetic fibres and the gland cells acetylcholine must of course be 

 able to mimic the action of nerve stimulation ; further, the quantity 

 of the agent set free must be big enough to excite the gland cells. 

 It is well known that acetylcholine evokes a secretion of saliva; and 

 the electrical responses to acetylcholine and to chorda stimulation 

 are identical, both in the external electrogram (Langenskiold, 1941) 

 and when intracellular recording is used (Lundberg, 1958). Com- 

 parisons between the composition of saliva obtained with different 

 stimuli is always difficult, particularly because the composition 

 varies with the rate of secretion ; the literature does not, however, 

 seem to contain any statements to the effect that there may be any 

 fundamental difference between saliva obtained with injected 

 acetylcholine and with parasympathetic stimulation. 



