226 INSTINCT: / 



of necessity, previously realized or imagined by the crea- 

 ture performing the acts, any more than the headless 

 frog realizes the ' end ' of movements which seem to us 

 to be distinctly purposive. It may, however, be otherwise. 



Thus in many Instincts an abiding visceral state (be- 

 getting, as it does, a corresponding appetite or desire) 

 exercises its powerful influence upon the higher nerve 

 centres generally, and so supplies a stimulus more or less 

 definitely realized prompting to a series of sensorially- 

 guided acts, which, owing to the similarities of the environ- 

 ments of individuals of each species, are subject to com- 

 paratively little variation in their successive steps. 



Broussais, following in the wake of Cabanis, was one 

 of the first to point out the great importance of visceral 

 states and impressions in reference to Instinctive Acts. 

 Citing a well-known, but important, illustration, he says :* 

 *' If, when a hen is impelled to incubation, we dip her 

 belly several times in cold water, the excitement dis- 

 appears, and the kind of clucking which accompanies this 

 desire ceases, together with all the other acts related to 

 the same end." And, that there are visceral causes or 

 states lying at the root of the sexual instincts generally, 

 may be inferred, among other things, from the fact that 

 in animals which have undergone certain mutilations such 

 instincts remain in abeyance. These states are only peri- 

 odically aroused in many animals, and in Birds, more espe- 

 cially, we find sexual changes forming part of the seasonal 

 rhythm of bodily states. " The pairing of animals usually 

 begins to take place in the spring ; when the winter is 

 passed, the earth is covered by verdure and adorned by 

 the various flowers that now expand their blossoms. . . . 

 The birds sing their love songs ; the nightingale is now 

 'most musical most melancboly'; the cuckoo repeats his 

 * "Traite de Physiologie," Pt. I., chap. viL 



