The methods of extraction used in separating the antipressor fraction from hepatic tissue are varied but simple. The original preparations were obtained by freezing and thawing the liver mash in Locke's solution and then removing the proteins and peptones from the saline extract. The present method involves the ues of boiling water in appropriate amounts and degrees of acidity and is much more effective. On the other hand, the problems of purification, standardization and stabilization are complex and are fraught with considerable difficulty.
The boiling acidulated aqueous extract is the most suitable method for the removal of the coagulable proteins. Acetic acid is quite effective, although other acids may be used, if due regard is had for the hydrogen ion concentration.
Throughout the entire procedure, it is necessary to prevent oxidation taking place in the extracts, as the active principle is apparently extremely labile and is readily destroyed. We are