56 Innervation of the Glandular Elements 



sympathetic impulses are able to reach all the secretory cells 

 susceptible to the sympathetic mediator (Emmelin, 19550). 



Which gland cells then have a sympathetic innervation? (In the 

 following the cells will be called "innervated" even if the effect is 

 an indirect one, as discussed above.) The problem whether the 

 individual gland cell is controlled both by parasympathetic and 

 sympathetic fibres has been a matter of dispute since the days of 

 Heidenhain and Langley. Through the work of Babkin and his 

 school it has been generally accepted that the gland cell is not 

 innervated by both sets of fibres, but that the alveolar cells have a 

 parasympathetic, the demilune cells a sympathetic supply. The 

 experimental evidence supporting this conception has been sur- 

 veyed by Babkin (1950). Recently, however, this view has been 

 contested by several investigators. 



Langenskiold (1941) analysed the external electrograms obtained 

 from the submaxillary gland on stimulation of the different nerves 

 and on injection of drugs, and came to the conclusion that "all 

 secretory cells in the submaxillary gland that are innervated by the 

 sympathetic are also innervated by the chorda". 



From histological investigations Glimstedt and Hillarp (1942) 

 concluded that the separate secretory cells of the rat's submaxillary 

 gland very likely have a double innervation. 



Experiments on the maximal rate of secretion under various con- 

 ditions have supported the view expressed by Langenskiold (Em- 

 melin, 19550). Stimulation of the cervical sympathetic trunk usually 

 causes an abundant flow of saliva from the submaxillary gland of 

 the cat. Nevertheless, when chorda stimulation elicits its maximal 

 rate of salivary flow, an added sympathetic stimulation is unable 

 to accelerate the flow further ; provided that the sympathetic fibres 

 were able to throw into activity cells not already activated by the 

 mediator released at the chorda endings, one would expect the flow 

 of saliva to increase. Fig. 3.6 shows such an experiment. The 

 maximal rate of flow obtained on chorda stimulation is shown in 

 the first section, that obtained on sympathetic stimulation in the 

 second. In the last part sympathetic stimulation was superimposed 

 upon the chorda stimulation; the rate of flow did not increase, but 

 after a short period it started to decrease. This latter effect is due to 

 sympathetic vasoconstriction. When the gland is secreting at a 

 maximal rate it is very susceptible to a reduction of the blood 

 supply. The vasoconstriction could be almost abolished by pre- 



