CHAPTER XIV. 



INSTINCT : ITS NATURE AND ORIGIN. 



WE may, without much difficulty, convince ourselves that 

 certain muscular actions are habitually going on within 

 our bodies in a more or less continuous fashion, indepen- 

 dently of Will, and even without arousing our Conscious- 

 ness. To this class belong the movements of the Heart. 

 Again, we may learn that other internal muscular actions, 

 equally independent of Will and free from conscious 

 accompaniment, take place in a distinctly intermittent 

 fashion. To this class belong those contractions of the 

 Stomach and Intestines which occur during the digestion 

 and assimilation of food. Again, we may learn that still 

 other internal contractions such as those concerned in 

 oviposition or in the birth of young recur at much longer 

 intervals, though they are similarly independent of Will 

 and uninstigated by conscious impressions. 



Other and wider muscular actions, partly internal and 

 partly external, also take place in a rhythmical manner in 

 relation with systemic conditions. The motions of the dia- 

 phragm and of the thoracic and abdominal walls, in con- 

 nection with Eespiration, belong to this category. These 

 movements, though in the main independent of Will, are 

 capable of being very considerably modified thereby ; and 

 while they are most frequently unheeded, they have a very 

 recognizable accompaniment of feeling when attention is 

 distinctly turned to them. 



