THE CIRCULATION. 



in 



which all the blood must pass ; the one, a shorter circuit 

 from the heart to the lungs and back again ; the other and 

 larger circuit, from the heart to all parts of the body and 

 back again ; but more strictly speaking, there is only one 

 complete circulation, which may be diagrammatically repre- 

 sented by a double loop, as in the accompanying figure. 



On reference to 

 this figure and 

 noticing the di- 

 rection of the ar- 

 rows which repre- 

 sent the course 

 of the stream 

 of blood, it will 

 be observed that 

 while there is a 

 smaller and a 

 larger circle both 

 of which pass 

 through the heart, 

 yet that these are 

 not distinct, one 

 from the other, 

 but are formed 

 really by one con- 

 tinuous stream, 

 the whole of 

 which must, at 

 one part of its course, pass through the lungs. Subor- 

 dinate to the two principal circulations, the pulmonary and 

 systemic as they are named, it will be noticed also in the 

 same figure, that there is another, by which a portion 

 of the stream of blood having been diverted once into 

 the capillaries of the intestinal canal, and some other 

 organs, and gathered up again into a single stream, is a 

 second time divided in its passage through the liver, 



Fig. 32. Diagram of the circulation. 



