OF THE INVERTEBRATE ANIMALS. 43 



mentum for the sake of convenience, we cannot explain a single 

 motor phsenomenon, much less a sum of them. This funda- 

 mental idea of Reil's excellent position regarding the so-called 

 vital foi-ce, " that it is the necessary result of form and compo- 

 sition," will remain as the sure basis of a rational physiology 

 {i. e. the physics of the organism). It was the identification of 

 the soul (the sum of the psychical motor phaenomena) with the 

 vital force (that of the physical) which necessarily led Reil, an 

 inductive philosopher, into numerous conclusions contradictory 

 to experiment: — with him physiology and psychology were syno- 

 nymous. 



We see that the mechanism of the organism in the simplest 

 vegetable form {Conferva, Protococcus) proceeds ad infinitum 

 with mathematical precision ; just as a curve according to its 

 formula, if but a differential of magnitude be given. But in the 

 animal world we find a substance added, the mechanism of 

 which we call psychology, a sum total of motor phaenomena 

 with as many points of commencement, directions and intensi- 

 ties, as there are reacting masses of the corporeal organism ; 

 like this, developing itself from a differential in magnitude ac- 

 cording to stated formulae, which formulae being pecuUar to each 

 species, according to the magnitude of the substituted value and 

 the duration of the real construction, admit in it of an infinite 

 variety. 



The only rational difference which we can make between an 

 animal and a plant, appears to me this ; that for each species of 

 plant we have from the commencement (which it is the province 

 • of geology and palaeontology to determine) one differential of 

 magnitude and one formula (cell), truly only a single differential, 

 for this by integration produces only one definite curve, be the 

 substituted values ever so different ; whilst in the animal two of 

 them are given (the cell plus the soul-atom), the integrals of 

 which we designate vegetable life in the former and animal life 

 in the latter. 



