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SCIENCE 



[N. S. Vol. XLII. No. 1074 



the blood are returned. We have named 

 the procedure plasmapheresis. 



It is apparent that when blood-letting is 

 practised in the usual way there is always 

 the risk of greatly reducing the oxygen- 

 carrying capacity of the blood through loss 

 of red corpuscles, but in our experiments 

 the fluid of the blood can be withdrawn in 

 large quantities without affecting this 

 capacity, as far as we can determine at the 

 present moment. Just how large quantities 

 of plasma can be withdrawn without per- 

 manent injury can not at present be stated. 

 In certain cases very large amounts have 

 been successfully removed in experiments 

 extending over several days. We have actu- 

 ally withdrawn from a dog by repeated 

 bleedings in a single day, a volume of blood 

 more than twice that contained in the body, 

 with no apparent injury, by our method of 

 returning the corpuscles after each bleed- 

 ing. How far this exceeds the quantity of 

 blood that may be safely removed from a 

 dog at one time without return of cor- 

 puscles is seen when we recall that the loss 

 at one time of 60 to 70 per cent, of the 

 animal's blood is quickly fatal. 



It may yet be possible to attach an elec- 

 trically controlled centrifugalizing appa- 

 ratus directly to the blood vessels of an 

 animal and tap off a desired quantity of 

 the fluid part of the blood while directing 

 the stream of corpuscles back into the body 

 (or vice versa), the whole apparatus being 

 analogous in a way to the modem cream 

 separator. 



It has been our purpose in our recent ex- 

 periments to find the limits to which the 

 plasmapheresis may be carried and to learn 

 what pathological changes ensue when the 

 procedure is carried to a point beyond 

 which life is endangered. With the form of 

 Locke's solution now employed by us, we 

 have in the course of five days carried the 

 removal of plasma to a point where the 



total volume of blood withdrawn from the 

 body equals at least five times that ordi- 

 narily contained in the body. In this ex- 

 periment the limit of the procedure was 

 probably reached, as the animal was very 

 nearly lost during the last bleeding; only 

 the speedy return of the sedimented cor- 

 puscles saved the dying animal. Unfortu- 

 nately, one can not conclude from these most 

 successful experiments that similar or even 

 markedly lower quantities can always be 

 removed without danger. We have re- 

 cently carried out a large number of ex- 

 periments with a view to determine the safe 

 limits of plasmapheresis both as to quan- 

 tity per day and total quantity of blood 

 withdrawn, but unfortunately these experi- 

 ments are vitiated by an error which has 

 only recently been discovered. It has been 

 found that the imported hirudin which we 

 are now using is strongly toxic. This was 

 not the case with the product which we 

 ourselves manufactured and which was 

 used in our earlier experiments. Further 

 experiments will have to be done, therefore, 

 to settle this question. 



Some interesting results have been ob- 

 tained by studying the chemical changes 

 during plasmapheresis. Since the method 

 consists essentially in replacing the plasma 

 of the blood by a saline solution, it is nat- 

 ural to find a decrease in the soluble pro- 

 teins of the blood. While not as rapid as a 

 purely mathematical calculation based on 

 the amounts drawn off and returned would 

 indicate, if the vascular system were re- 

 garded as a vessel of given capacity to be 

 washed out, the decrease is considerable. 

 In three days the soluble proteins have been 

 reduced to about one third their original 

 value, after which there is a slight rise as 

 the process is continued. Evidently, as was 

 expected, there is a continual renewal of 

 plasma proteins from the tissues. 



In striking contrast to this, the non- 



