XIV INTRODUCTORY REMARKS. 



men devoted their labours to its promotion, both 

 in the observation of facts and in systematic arrange- 

 ment. At this period, Linnaeus, taking, as his great 

 predecessor had done, the circulatory system as the 

 foundation of his arrangement, distributed animals 

 into three great divisions, each containing two classes, 

 viz. : 



I. Such as have a heart with two auricles and 

 two ventricles ;* the blood warm and red ; contain- 

 ing, 



Class 1. Such as produce living young Mammalia. 

 2. Such as produce eggs Aves. 



II. Such as [he supposed to] have a heart with 

 but one auricle and one ventricle ; the blood cold 

 and red ; containing, 



Class 3. With the lung voluntary Amphibia. 

 4. With gills instead of lungs Pisces. 



III. Such as have a heart with a single auricle 

 and no ventricle ; a cold and white fluid in the 

 place of blood ; containing, 



Class 5. Such as have antennaef Insecta. 

 6. Such as have tentaculaj Vermes. 

 These six Classes he divided into Orders ; founding 

 his characters chiefly on the organs of eating, and 

 those of motion. The Mammalia were characterized 

 by the number, form, and position of the teeth ; 

 the Birds, by the form of the beak and feet ; the 



* The auricles are bags at the base of the heart, which receive the 

 blood from the veins ; the ventricles are the large cavities of the heart, 

 which drive the blood into the arteries. 



f Jointed organs projecting from the head. 



Fleshy projections, not jointed. 



