172 LAMARCK, HIS LIFE AND WORK 



which then passes along the smallest nervous ramifi- 

 cations in the substance of the nerve, which is a very 

 good conductor for it. On its side the brain sends 

 back the subtile fluid in question along the nerves to 

 the different organs. 



In the same work (1802) Lamarck defines thought 

 as a physical act taking place in the brain. "This 

 act of thinking gives rise to different displacements 

 of the subtile nervous fluid and to different accumula- 

 tions of this fluid in the parts of the brain where the 

 ideas have been traced." There result from the flow of 

 the fluid on the conserved impressions of ideas, special 

 movements which portions of this fluid acquire with 

 each impression, which give rise to compounds by 

 their union producing new impressions on the delicate 

 organ which receives them, and which constitute 

 abstract ideas of all kinds, also the different acts of 

 thought. 



All the acts which constitute thought are the com- 

 parisons of ideas, both simple and complex, and the 

 results of these comparisons are judgments. 



He then discusses the influence of the nervous fluid 

 on the muscles, and also its influence considered as 

 the cause of feeling {sentiment). Finally he concludes 

 that feu fix^, caloric, the nervous fluid, and the 

 electric fluid " are only one and the same substance 

 occurring in different states." 



