74 Pharmacology of Salivary Secretion 



after a few cigarettes is insufficient to cause secretion (Schnedorf 

 and Ivy, 1939). 



The secretion caused by ether, chloroform or cyclopropane is 

 likewise of reflex origin. Robbins (1935) examined the effect of 

 various anaesthetics on the parotid secretion in dogs. With the 

 agents mentioned he observed a lively flow of saliva when they 

 were first administered; in deep anaesthesia the flow ceased, to 

 return during recovery. No secretion was obtained if the agents 

 were supplied directly via a tracheal cannula, or if the upper 

 respiratory tract had been cocainized ; the site of action was, there- 

 fore, assumed to be on nerve endings in the upper respiratory 

 mucosa. During surgical anaesthesia, the reflex was suppressed by 

 the action of the anaesthetics on the medullary centres. 



A reflex which may be related to the one just described has been 

 observed by Elsberg, Spotnitz and Strongin (1940, 1942). Flow of 

 saliva elicited from the nasal mucosa by odorous substances is 

 generally assumed to be due to a conditioned reflex ; these authors, 

 however, studied a response which they called the olfactory- 

 parotid reflex and supposed to be unconditioned. When a stream 

 of air containing menthol or phenylethyl alcohol was blown into the 

 nose, saliva was found to flow from the parotid glands, particularly 

 ipsilaterally. The response was obtained even in patients with com- 

 plete anosmia and was therefore assumed to be elicited from end- 

 ings of trigeminal fibres. This is in agreement with the conclusions 

 reached by Lashley (1916) according to whom there is no uncon- 

 ditioned reflex secretion to olfactory stimulation, whereas odorous 

 substances, which irritate the mucosa, like amyl alcohol or oil of 

 peppermint, may stimulate salivary secretion. 



Numerous early investigators have stated that a solution of 

 atropine can cause a flow of saliva when dropped into the eye. This 

 effect is, however, not elicited from the conjunctiva as once sup- 

 posed but from the oral mucosa (Metzner, 191 2; Blume, 1928). 



DRUGS WITH CENTRAL ACTIONS 



Salivary secretion may be one of the effects caused by drugs that 

 excite the central nervous system. For instance, picrotoxin in a 

 dose which gives convulsions and stimulates the medullary respira- 

 tory and circulatory centres evokes a flow of saliva as well (Griin- 

 wald, 1909). After bulbocapnine in sublethal or lethal doses, salivary 

 secretion was observed (Amadon and Craige, 1935). Tournade and 



