206 
FOURTEENTH REPORT. 
THE MOUTH REFLEX OF PHYSA ; MAY IT BE SUBSTITUTED 
FOR THE SALIVARY REFLEX OF PAWLOW IN STUDIES 
OF THE NERVOUS SYSTEM OF SNAILS * 
ELIZABETH L. THOMPSON. 
Although the salivary reflex method as developed by Pawlow has 
been used quite extensively in the study of animal behavior in Russia 
and Germany, nothing has been done on it in America. Prof. J. P. 
Pawlow, Director of the Physiological Department of the Institute of 
Experimental Medicine in St. Petersburg, devised the method in his 
work on the relations existing between the physiology of the central 
nervous system and the psychic reactions of animals, known as animal 
behavior. Dogs were used in the experiments but the method is ap- 
plicable to other similar mammals. The method of procedure was 
briefly as follows. The duct of a salivary gland, preferably a parotid, 
was opened on the outside through a fistula. Over the opening was 
cemented a funnel leading into a graduate so that the secretion of the 
gland could be readily collected and measured. In a later investigation 
carried on by one of Pawlow’s students ( Selionyi) , a rubber tube was 
attached to the funnel and this carried the saliva to a tambour and 
each drop was thus recorded upon a smoked drum. 
When the salivary gland is stimulated by food to secrete, the reaction 
thus produced is termed an “unconditional reflex.” When this “uncon- 
ditional reflex” has been definitely measured bv determining the amount 
of saliva produced, another stimulus such as color or sound is applied 
simultaneously with the food stimulus. After the association has been 
established the color or sound is used as a stimulus in the absence of 
food and a flow of saliva obtained. This is called a “conditional reflex.” 
The glandular secretion being entirely involuntary affords an exact 
measure of the effect of the stimulus on the nervous system which 
trols the salivary glands, giving the experiment a physiological as well 
as a psychological basis. 
Pawlow and his students believe that the method can be worked 
out on only a limited number of mammals. But a similar method is 
applicable to any organism having a measurable, involuntary muscular 
action or secretion, definitely effected by external stimulation. 
Such a movement was believed by Prof. Reighard to occur in the 
mouth parts of the fresh water snail Physa, and work is now in progress 
under his direction. These snails often cling to or crawl upon the 
under side of the surface film for an indefinite length of time, with the 
shell below the surface and the ventral side of the body or the foot 
exposed to view. The mouth, which is on the ventral side, opens and 
closes frequently a hundred or more times in succession, the reaction 
probably occurring as the result of stimulation caused by microscopic 
*Yerkes and Morgulis: The Method of Pawlow in Animal Psychology. Psychological Bulletin, 
Vol. VI, No. 8. Aug. 15, 1909. 
