334 LAMARCK, HIS LIFE AND WORK 



constitute all the acts of instinct ; and as these acts 

 are not the result of deliberation, of choice, of judg- 

 ment, the actions which arise from them always 

 satisfy, surely and without error, the wants felt and 

 the propensities arising from habits. 



" Hence, instinct in animals is an inclination which 

 necessitates that from sensations provoked while 

 giving rise to wants the animal is impelled to act 

 without the participation of any thought or any act 

 of the will. 



" This propensity owes to the organization what 

 the habits have modified in its favor, and it is excited 

 by impressions and wants which arouse the organic 

 sense of the individual and put it in the way of send- 

 ing the nervous fluid in the direction which the pro- 

 pensity in activity needs to the muscles to be placed 

 in action. 



" I have already said that the habit of exercising 

 such an organ, or such a part of the body, to satisfy 

 the needs which often spring up, should give to the 

 subtile fluid which changes its place where is to be 

 operated the power which causes action so great a 

 facility in moving towards this organ, where it has 

 been so often employed, that this habit should in a 

 way become inherent in the nature of the individual, 

 which is unable to change it. 



" Moreover, the wants of animals possessing a ner- 

 vous system being, in each case, dependent on the 

 structure of these organisms, are : 



"I. Of obtaining any kind of food ; 



" 2. Of yielding to sexual fecundation which excites 

 in them certain sensations ; 



" 3. Of avoiding pain ; 



" 4. Of seeking pleasure or happiness. 



" To satisfy these wants they contract different 

 kinds of habits, which are transformed into so many 

 propensities, which they can neither resist nor change. 

 From this originate their habitual actions, and their 



