110 VASCULAR SYSTEM. 



Q. What are the general uses of the circulation with 

 black blood? 



t/?. It is a reservoir for the various substances, from 

 within and without, which enter into the venous blood, 

 such as the fluids from the lymphatics, from the thoracic 

 duct, the chyle, &c. 



Q. Under what circumstances will the chylous vessels 

 take up deleterious substances? 



/?. If the organic sensibility is altered or exalted, these 

 vessels will receive that which in health they would re- 

 ject. Thus it is with the skin, when it absorbs matters, 

 and they go into the black blood circulation. 



Q. Bring the circulations into nearer relation. 



#. The circulation of black blood receives materials 

 into the system, while that of red blood expends them 

 on it. 



Q. How does this explain plethora? 



/?. If the black blood circulation receives more than the 

 red blood expends, there is plethora; on the contrary, an 

 impoverished state of the humours shows itself when the 

 red blood expends more than the black blood receives. 



Situation, Forms, and General Arrangement of the 

 Vascular 'System. 



Q. Why does gangrene more frequently appear in the 

 lower extremities, than in the head and upper extremities? 



*ft. Because in the lower extremities the impulse of the 

 heart in the circulation is weakened, and the free return 

 of blood is opposed by gravity. 



Q- How is the aorta united to the heart? 



