314 The Animal Mind 



simultaneously? We may quote from Jennings the facts 

 about Paramecium. "If the animal is at rest against a 

 mass of vegetable matter or a bit of paper, . . . and it 

 is then struck with the tip of a glass rod, we find that at first 

 it may not react to the latter stimulus at all." "A strong 

 blow on the anterior end causes the animal to leave the solid 

 and give the typical avoiding reaction." "If specimens 

 showing the contact reaction are heated, it is found that they 

 do not react to the heat until a higher temperature is reached 

 than that necessary to cause a definite reaction in free-swim- 

 ming specimens." "On the other hand, both heat and cold 

 interfere with the contact reaction. Paramecia much above 

 or much below the usual temperature do not settle against 

 solids with which they come in contact, but respond in- 

 stead by a pronounced avoiding reaction." "Specimens in 

 contact with a solid react less readily to chemicals than do 

 free specimens. . . . On the other hand, immersion in 

 strong chemicals prevents the positive contact reaction." 

 "The contact reaction may completely prevent the reaction 

 to gravity," and to water currents. It also modifies the re- 

 action to the electric current. While a part of the influence 

 exerted by the contact reaction on other responses may be 

 purely physical, due to the fact that an actual secretion of 

 mucus may occur whereby the animal "sticks fast" to the 

 solid, yet this alone does not explain the facts, for the cilia 

 that are not attached do not behave normally. The 

 reaction to gravity regularly yields whenever opposed to 

 the action of any other stimulus (378, pp. 92 ff.). 



Sometimes the action of one form of stimulation merely 

 affects the form of the response to another, as in the case 

 where abnormal temperature causes the avoiding instead 

 of the positive reaction to be given to solids. In other cases, 

 reaction to one of the stimuli is suppressed or weakened. 



