It has been found that when arsphenamin is mixed either in vivo or in vitro with blood, marked changes occur in the properties of certain of the proteins of the plasma.1 The fibrinogen becomes incoagulable to both heat and thrombin. Preliminary experiments have shown that these proteins are in no sense "destroyed," as they may be precipitated by carbon dioxid along with the arsphenamin. These phenomena are similar in nature to the changes in the properties of the globulins when acted on by alkali, and although it has been shown that the hydroxyl ions are not alone responsible for these alterations in our experiments, it may be that arsphenamin reacts in an analogous way with the proteins. If such were the case, a union of protein and arsphenamin would occur. The present study is an examination of this possibility.
Closely related to the main object of this study is