Secretory Fibres through other Channels 65 



without success. The conditioned responses obtained, very quickly 

 elicited, surely suggest the existence of some nervous pathway. 

 Koropow (1939) found the salivary reflex of the parotid gland of 

 dogs to reappear some time after parasympathetic denervation; 

 sympathetic denervation did not abolish the response. Similar 

 results were described by Emmelin and Stromblad (1953), working 

 on dogs with permanent fistulae of the submaxillary glands. Con- 

 ditioned reflexes were obtained from the "denervated" glands; 

 they were initially very small but increased gradually in the course 

 of time ; after some weeks when they had fully developed on one 

 side, the contralateral gland gave as big a response only a few days 

 after "denervation". Babkin (1950) suggests that "reserve paths" 

 may exist which after section of the usual secretory nerves gradu- 

 ally take over their function. 



Some observations in man may be further quoted. In three 

 patients Reichert and Poth (1933) observed that the flow of saliva 

 diminished not only from the parotid, but from the submaxillary 

 and sublingual glands as well after intracranial section of the glos- 

 sopharyngeal nerve ; this was followed by some recovery. Similarly, 

 section of the chorda in the middle ear decreased the secretion from 

 all three glands. The authors concluded that all the glands receive 

 secretory fibres from the seventh and the ninth nerves. In anatomi- 

 cal investigations in man Guerrier and Bolonyi (1948) have found 

 nerve fibres from a cervical branch of the facial nerve entering the 

 submaxillary gland, and fibres from the hypoglossal nerve which 

 enter the sublingual gland. Recently, Laage-Hellman and Strom- 

 blad (i960) have observed that no pronounced supersensitivity 

 develops in the submaxillary gland after section of the chorda in 

 the middle ear in patients. When searching for an explanation for 

 this they have found that a profuse reflex secretion can still be 

 obtained in these cases; the effect can be abolished by injecting 

 local anaesthetics with the aim of blocking the hypoglossal or 

 glossopharyngeal nerves. 



There are apparently great species differences in this respect. 

 Stimulation of the hypoglossal nerve in cats does not cause any 

 submaxillary secretion, even if the chorda has been cut in advance ; 

 this operation would otherwise in two ways favour the unveiling 

 of secretory fibres in the hypoglossal: by mobilizing the "reserve 

 path" and by sensitizing the gland cells to secretory impulses 

 (Emmelin, Muren and Stromblad, 1957a). 



P.S.G. — F 



