INTRODUCTION. 29 



There is no visible mark of instinct in the conformation of 

 the animal, but, as well as it can be ascertained, the intelligence 

 is always in proportion to the relative size of the brain, and 

 particularly of its hemispheres. 



Of Method, as applied to the Animal Kingdom. 



From what has been stated with respect to methods in ge- 

 neral, we have now to ascertain what are the essential charac- 

 ters in animals, on which their primary divisions are to be 

 founded. It is evident they should be those which are drawn 

 from the animal functions, that is from the sensations, and mo- 

 tions; for both these not only make the being an animal, but in 

 a manner establish its degree of animality. 



Observation confirms this position by showing that their 

 degrees of development and complication accord with those of 

 the organs of the vegetative functions. 



The heart and the organs of the circulation form a kind of 

 centre for the vegetative functions, as the brain and the trunk 

 of the nervous system do for the animal ones. Now we see 

 these two systems become imperfect and disappear together. 

 In the lowest class of animjils, where the nerves cease to be 

 visible, the fibres are no longer distinct, and the organs of 

 digestion are simple excavations in the honogeneous mass of 

 the body. In insects the vascular system even disappears 

 before the nervous one; but, in general, the dispersion of the 

 medullary masses accompanies that of the muscular agents : a 

 spinal marrow, on which the knots or ganglions represent so 

 many brains, corresponds to a body divided into numerous 

 rings, supported by pairs of limbs longitudinally distributed, 

 &c. 



This correspondence of general forms, which results from 

 the arrangement of the organs of motion, the distribution of the 

 nervous masses, and the energy of the circulating system, 

 should then bei the basis of the primary divisions of the animal 

 kingdom. We will afterwards ascertain, in each of these 

 divisions, what characters should succeed immediately to those, 

 and form the basis of the primary subdivisions. 



