In 1914 Abel, Rowntree and Turner1 reported on the physiologic effects in dogs of bleeding, removing the plasma and returning the corpuscles after washing with Locke's solution. Such a process was appropriately designated "plasmaphaeresis," and it was shown by these authors and by Turner, Marshall and Lamson2 that it could be carried to a very considerable extent with entire recovery of the experimental animal. The technic presented in these articles required the use of herudin for prevention of blood coagulation, and positive evidence was secured that the German preparation of herudin then on the market had toxic properties of high order.3 While the authors in question have offered a number of suggestions as to the possible practical use of plasmaphaeresis, the difficulty of the maneuver, coupled with the impossibility of using herudin, seems to have prevented its clinical employment. In the course of experiments designed to disclose the toxic elements