CH. XXV.] THE SPLEEN 335 



actually liberate haemoglobin; there is no free haemoglobin in thfe 

 blood-plasma of the splenic vein. 



(4.) The spleen participates in nitrogenous metabolism, especially 

 in the formation of uric acid (see Uric Acid formation in Chapter 

 on Urine). 



(5.) Besides these direct offices, the spleen fulfils some purpose 

 in regard to the portal circulation with which it is in close connec- 

 tion. From the readiness with which it admits of being distended, 

 and from the fact that it is generally small while gastric digestion is 

 going on, and enlarges when that act is concluded, it is supposed to 

 act as a kind of vascular reservoir, or diverticulum to the portal 





0. PRESSURE 



FJCJ. 278. The upper tracing is the spleen record; the next is carotid blood -pressure taken with a 

 mercurial kymograph. The straight line beneath this is the abscissa of the arterial pressure ; and 

 the lowest tracing is the time in seconds. 



system, or more particularly to the vessels of the stomach. This 

 mechanical influence on the circulation, however, can hardly be 

 supposed to be more than a very subordinate function. The main 

 use of the contractility of the spleen is to assist the passage of the 

 blood through itself. 



It has been found by experiment that when the splenic nerves 

 are cut the spleen enlarges, and that contraction can be brought 

 about by stimulation of the peripheral ends of the divided nerves. 

 If the splenic nerves are not cut, contraction is produced by 

 (1) stimulation of the spinal cord ; (2) reflexly by stimulation of 

 the central stumps of certain divided nerves, e.g., vagus and sciatic ; 

 (3) by local stimulation by an electric current; (4) by the admini- 

 stration of quinine and some other drugs. 



