8o The Animal Mind 



reaction takes a more violent form. 1 The time occupied in 

 reacting has, however, recently been made a basis for dif- 

 ferentiating the response to different chemicals. It was found 

 that if the worms were suspended by threads, and their an- 

 terior ends dipped into solutions of sodium, ammonium, 

 lithium, and potassium chlorides, the animals reacted to these 

 substances with diminishing promptness in the order just 

 given. The differences in reaction time were marked. Now 

 all four of these substances produce in man nearly the same 

 taste quality, salt, for which the common constituent chlorine 

 is therefore held responsible. The sodium, lithium, ammo- 

 nium, and potassium ions have apparently but little effect on 

 the human taste organs. Since the earthworm reacts with 

 decided time differences to the four, it may be that its taste 

 organs are specifically affected by each, and that different taste 

 Y qualities may be occasioned in its consciousness, supposing it 

 / to be conscious (314). In other members of the annelid family, 

 such as the leeches and marine worms, we know little of the 

 differentiation between food and contact senses. That some of 

 them respond to odorous substances is stated by Nagel (292). 



21. The Chemical Sense in Mollusks 



In the case of the Mollusca, also, there is little satisfactory 



r evidence on the subject of the chemical sense. The Acephala, 



to which the clam, oyster, and scallop belong, do not take 



1 W. W. Norman argued that the squirming reactions of worms, and 

 the corresponding reactions of other animals to injurious stimulation, can- 

 not be taken as evidence of an accompaniment of disagreeable conscious- 

 ness, because of the fact that when the worm, for instance, is cut in two, 

 the squirming movements are confined to the posterior piece, while the head 

 end crawls away undisturbed. The head end, he urges, containing the 

 cerebral ganglia, ought to be the part capable of suffering, but it gives no 

 reaction (295). We cannot, however, conclude from the absence of a reac- 

 tion under abnormal conditions that its possible conscious accompaniment 

 in the normal state is also done away with. 



