222 Heredity. 



clearer light If, after having cut off the head of a frog, we pinch 

 any part of its skin, the animal at once begins to move away, with 

 the same regularity as though the brain had not been removed. 

 Flourens took guinea-pigs, deprived them of the cerebral lobes, 

 and then irritated their skin : the animals immediately walked, 

 leaped, and trotted about, but when the irritation was discontinued 

 they ceased to move. Headless birds, under excitation, can still 

 perform with their wings the rhythmic movements of flying. But 

 here are some facts more curious still, and more difficult of explan- 

 ation. If we take a frog, or a strong and healthy triton, and sub- 

 ject it to various experiments; if we touch, pinch, or burn it with 

 acetic acid ; and if then, after decapitating the animal, we subject 

 it again to the same experiments, it will be seen that the reactions 

 are exactly the same ; it will strive to be free of the pain, to shake 

 off the acetic acid that is burning it ; it will bring its foot up to the 

 part of its body that is irritated, and this movement of the member 

 will follow the irritation wherever it may be produced. 1 We can 

 hardly say that here the movements are co-ordinated like those of 

 a machine ; the acts of the animal are adapted to a special end ; 

 we find in them the characters of intelligence and will, a know- 

 ledge and choice of means, since they are as variable as the cause 

 which provokes them. 



If, then, these and similar acts were such that both the impres- 

 sions which produce them and the acts themselves were perceived 

 by the animal, would they not be called psychological ? Is there 

 not in them all that constitutes an intelligent act, adaptation of 

 means to ends, not a general and vague adaptation, but a deter- 

 minate adaptation to a determinate end ? In the reflex action we 

 find all that constitutes, in some sort, the very groundwork of an 

 intelligent act that is to say, the same series of stages, in the same 

 order, with the same relations between them. We have thus in 

 the reflex action all that constitutes the psychologic act except 

 consciousness. The reflex act, which is physiological, differs in 

 nothing from the psychological act, save only in this, that it is with- 

 out consciousness. 



1 For further details see Vulpian, Pkysiologie du Systtme Nerveux, pp. 

 417 428 ; it will there be seen that headless animals act precisely as though 

 they had heads. See also Despine, Psychologie Naturdle, tome i. ch. vii. 



