244 PHYSIOLOGY AT THE FAKM. 



(3) functions of relation. No such method can be rigidly 

 perfect ; nevertheless this arrangement is very useful. The 

 circulation of the blood, respiration, digestion, secretion, ex- 

 cretion, are examples of the functions of assimilation, as all 

 these and some others are directly or indirectly concerned in 

 the development, growth, and maintenance of the living system. 

 The functions of reproduction are those concerned in the con- 

 tinuance of the species. The functions of relation are those 

 which connect the animal with the world without the functions 

 of knowledge and power ; that is, the functions by which the 

 animal becomes acquainted with external things, and acquires 

 power over the same. Such functions are manifestly the senses 

 and the muscular actions on which bodily activity depends. 



Circulation of the Blood. The parts concerned in the cir- 

 culation of the blood are the heart, the arteries, and the veins. 

 The heart consists of two sides, between which there is no 

 direct communication namely, the left side and the right side ; 

 and each side contains two cavities namely, an auricle and a 

 ventricle ; and between each auricle and the corresponding 

 ventricle there is a free communication. As to the arteries, 

 there are two great arterial systems, between which there is 

 no immediate communication or connection ; namely, the aorta 

 and its extensive ramifications, and the pulmonary artery with 

 similar ramifications. As to veins, there are also two great 

 venous systems, between which there is no immediate com- 

 munication or connection; namely, the system of the vence cavce 

 and their numerous ramifications, and the system of the pul- 

 monary veins with like ramifications. 



There are two kinds of blood, the red and the black ; that is, 

 the bright red and the dark red. The red is called the arterial 

 blood, but it exists only in one of the arterial systems namely, 

 in that of the aorta ; the black is called venous blood, but it 

 exists only in one of the venous systems namely, that of the 



