48 NATURAL HISTORY. 



As regards the red-blooded or Vertebrate animals, the 

 structure of the ventricle of the heart is taken in the 

 above classification as the primary element of the arrange- 

 ment. Hence the first thing which Ray himself would 

 have done, in dealing with some Vertebrate animal which 

 he did not know, would have been to examine its heart. 

 If it had a double ventricle, he would have concluded 

 that it must belong to the Cetaceans (whales, dolphins, 

 &c.), the ordinary terrestrial quadrupeds, or the birds. 

 If it had a single ventricle, he would have placed it either 

 among the reptiles (under which name he included both 

 the true Reptiles and the Amphibians), or among the 

 fishes. Supposing the animal to belong to the first series 

 that is, to the groups with a double ventricle Ray would 

 have next investigated the method in which it brought 

 forth its young. If it were viviparous, he would have his 

 further choice restricted to the two groups of the Cetaceans 

 and the ordinary Mammals ; if it were oviparous, he would 

 be able to place it definitely among the birds. In the case 

 of its being viviparous, the only character which would be 

 consulted would be whether it lived in the water or upon 

 the land. If it were an aquatic animal, Ray would locate 

 it finally among the Cetaceans ; whereas it would find a 

 place among the ordinary quadrupeds, if its habits were 

 terrestrial. 



Now this classification, though sufficiently convenient 

 when there is no particular object in view other than simply 

 to discover to what great group a given Vertebrate animal 

 is to be referred, is an eminently * artificial' arrangement. 

 That is to say, the characters used to separate the different 

 groups are to a large extent non-essential ones, and do 



