50 Innervation of the Glandular Elements 



as shown by the straight line of the figure (a cumulative drop 

 record). Sympathetic stimulation increases the rate of flow; but 

 this is followed by a compensatory decrease in the rate. Experi- 

 ments by these authors showed that the total amount of saliva col- 

 lected over a 30-min period with stimulation for 20 sec of every 

 2 min was not bigger than that discharged during the same period 

 without stimulation. 



Kuntz and Richins (1946) examined histologically the question 

 of the innervation of the myoepithelial cells of the parotid and sub- 



1401 



I 



SO 

 JO 



45" cervical sympathetic 

 stimulation commencing 

 at 3 min 



5 6 7 

 Time, min 



Fig. 3.3. The effect of cervical sympathetic stimulation upon the basal flow of 

 saliva in a parotid gland of a sheep. 



Parasympathetic fibres divided. The gush of saliva obtained on sympathetic stimulation is 

 compensated for in the subsequent pause (Coats, Denton, Goding and Wright, 1956). 



maxillary glands of cats, dogs and monkeys; the different nerves of 

 the glands were cut and left to degenerate. From this investigation 

 it was concluded that the myoepithelial cells are innervated ex- 

 clusively through the parasympathetic nerves. The discrepancy 

 between these observations and those described above has not been 

 explained. The physiological evidence surely strongly supports the 

 view that there are sympathetic motor fibres which are able to 

 activate some kind of contractile mechanism in the salivary glands. 

 Such motor fibres may alone be responsible for a flow of saliva 

 following sympathetic stimulation in some types of glands (or an 

 accelerated flow, as in the sheep's parotid gland, for instance). In 



