Response of Arteries to Blood Serum and Plasma. 85 



serum are not identical in their physiological activities, for, 

 whereas the effect just described is produced by serum, plasma 

 is entirely inactive. The process of clotting liberates some 

 substance to which this action is to be attributed. 



It was probably these experiments of Brodie which guided 

 O'Connor in the analysis of the constrictor effect produced by 

 blood serum on the hind limbs of the frog. He was able to show 

 that the constriction produced by serum is not entirely due to its 

 suprarenin content. Another substance comes into play which 

 causes constriction and which is present only in the serum. 



We have investigated the vasomotor effect of plasma and 

 serum in different vessels of the body, especially in regard to their 

 mode of action. 



The methods we employed were the perfusion of the organ 

 with Ringer's solution in a moist atmosphere at the temperature 

 of the body and under a constant pressure. The outflow from 

 the vein was recorded with a signal magnet writing on a smoked 

 paper. Two c.c. of serum or hirudin plasma were injected close 

 to the canula inserted in the artery. 



Effect of serum. — The typical effect when injected into the 

 vessels of the limb is to produce an immediate diminution in the 

 rate of outflow. This usually lasts for from five to ten seconds, 

 when it gradually begins to return to normal. The original rate 

 of flow is regained in about five minutes. 



A similar result is obtained when the heart is perfused. 



Entirely different is the effect which is produced when 2 c.c. 

 of serum are injected into the vessels of the perfused kidney. 

 Instead of a vasoconstriction there is produced a pronounced 

 vasodilatation. 



We have first to determine whether the dilatory effect on the 

 kidney and the constrictor effect on the limb vessels are due to 

 the same substance. It can readily be shown that two substances 

 are operating. If the serum is boiled and filtered through a 

 Berkfeldt filter and injected we now get no dilatation of the 

 kidney vessels, but instead a constriction. 



As before, the effect of boiled serum is to produce a constriction 

 of the limb vessels. 



Precipitation of the protein constituents of serum by alcohol 



