60 Innervation of the Glandular Elements 



sympathetic stimulation has been much less studied than the medi- 

 ator of the parasympathetic fibres. Since the investigations by 

 Cattell, Wolff and Clark (1934) the sympathetic fibres of the sali- 

 vary glands have been supposed to be adrenergic. These workers 

 showed that stimulation of the sympathetic fibres of the gland 

 caused a contraction of the sensitized contralateral nictitating mem- 

 brane ; this effect could not be induced if the venous effluent from 

 the gland had been stopped by a clamp. The effect could, of course, 

 be due to sympathin from the vasoconstrictor endings in the 

 gland, and it probably was in part. It was, however, further demon- 

 strated that the secretory effects of sympathetic stimulation were 

 increased by cocaine, which indicated an adrenergic transmitter at 

 work. The fact that the electrical responses to adrenaline are iden- 

 tical with those obtained on sympathetic stimulation may further 

 speak in favour of the view that the transmission is adrenergic. 

 Whether the transmitter is adrenaline, noradrenaline or both, is not 

 known, and probably difficult to establish in view of the fact that 

 the nerve seems to contain not only secretory, but motor and vaso- 

 motor fibres as well. Oborin (1954) perfused the submaxillary gland 

 of the cat and found that both adrenaline and noradrenaline ap- 

 peared in the perfusate on sympathetic stimulation. The greater 

 part of the sympathin was noradrenaline, but at least 10 per cent 

 was adrenaline. Smaller doses of adrenaline are needed to produce 

 a secretion than of noradrenaline ; in many cats the secretory effect 

 of adrenaline is but little increased by cocaine, but that of nor- 

 adrenaline markedly, and in these animals cocaine has only a small 

 effect on the secretory response to sympathetic stimulation (Em- 

 melin and Emmelin, 1953). These observations may centre the 

 interest on adrenaline as a transmitter for the secretory process : but 

 further work on this problem is certainly required. 



Very little is known, likewise, about the destruction of the secre- 

 tory mediator in the salivary glands. It may be mentioned here that 

 amine oxidase has been shown to be present. The submaxillary 

 gland of the cat shows a higher activity than the parotid gland ; in 

 that connection it is pointed out that the sympathetic secretory 

 innervation is much more pronounced in the former gland than in 

 the latter. Removal of the superior cervical ganglion does not cause 

 a fall in the amine oxidase activity in the submaxillary gland, and 

 in the parotid gland there is even an increased activity (Stromblad, 

 19566). 



