52 THE CIRCULATION OF THE BLOOD 



pathetic system, but these ganglia are influenced by the cells 

 in the vaso-motor center. 



Amount of Blood Important. When there is a small loss 

 of blood from a slight injury the entire vascular system con- 

 tracts and the current supplying this diminished area is 

 sufficient; but at other times the loss of blood is so great that 

 the amount remaining is not sufficient to carry on a complete 

 circulation. Unless remedied this results in death. In such 



FIG. 27. Capillaries. 



The outlines of the nucleated endothelial cells with the cement blackened by the 

 action of silver nitrate. (Landois.) 



cases of great loss the deficit may be supplied by a normal 

 salt solution, thus giving an amount of fluid sufficient to 

 maintain the heart action. But in cases where as much as 

 two-thirds of the blood is lost, the injection of fluid does no 

 good. The amount of fluid necessary to cause the heart's 

 action to continue may be supplied, but the amount of hemo- 

 globin necessary for life is lost and this cannot be sup- 

 plied. Asphyxiation is the result. 



