6o 



PHYSIOLOGY. 



channel varies considerably in width and depth. Where 

 the channel is large, whether from increased width or depth, 

 there the current is slower, but wherever the channel is 

 reduced, the current is more rapid. So the stream in 

 the relatively narrow artery is swift. In the capillaries, 



Pulmonary Vein - \ 



Digestive Tube 



Pulmonary Artery 

 Lymph Vein 



Right Auricle 

 Right Ventricle 

 Cava) Vein 



- Liver 



Fig. 28. Plan of Circulation. (Dorsal View.) 



although any individual channel is small, these channels 

 all together are wide ; the result is the same whether a 

 river widens out into a single lake, or divides into a great 

 number of channels running past innumerable islands, 



