492 HISTORY OF PHYSIOLOGY. 



Sect. 2. Distinction of the General Types of the 

 Forms of Animals. Cuvier. 



ANIMALS were divided by Lamarck into vertebrate 

 and invertebrate ; and the general analogies of all 

 vertebrate animals ar*e easily made manifest. But 

 with regard to other animals, the point is far from 

 clear. Cuvier was the first to give a really philoso- 

 phical view of the animal world in reference to the 

 plan on which each animal is constructed. There 

 are 8 , he says, four such plans; four forms on 

 which animals appear to have been modelled ; and 

 of which the ulterior divisions, with whatever titles 

 naturalists have decorated them, are only very 

 slight modifications, founded on the developement 

 or addition of some parts which do not produce 

 any essential change in the plan. 



These four great branches of the animal world 

 are the vertebrata, mollusca , articulata, radiata ; 

 and the differences of these are so important that a 

 slight explanation of them may be permitted. 



The vertebrata are those animals which (as man 

 and other sucklers, birds, fishes, lizards, frogs, ser- 

 pents,) have a back-bone and a skull with lateral 

 appendages, within which the viscera are included, 

 and to which the muscles are attached. 



The mollusca, or soft animals, have no bony 

 skeleton ; the muscles are attached to the skin, 

 which often includes stony plates called shells; 



8 Regne Animal, p. 57. 



