July 30, 1915] 



SCIENCE 



145 



move from the blood flowing througli it all 

 traces of these substances as fast as they 

 are poured into it, without at the same time 

 removing proteids or the indispensable 

 cellular elements (erythrocytes, leucocj^tes, 

 etc.) of the blood. Such an apparatus 

 might conceivably be employed also in an 

 emergency in certain toxic states in which 

 the eliminating organs, more especially the 

 kidneys, can not act rapidly enough to re- 

 lieve the system. 



An apparatus of this kind was con- 

 structed with the skilful assistance of Dr. 

 Turner. Essentially, the method consists 

 in connecting an artery or a vein of 

 the animal by a cannula to an apparatus 

 made of celloidin or other dialyzing mem- 

 brane, in the form of tubes, immersed in a 

 saline solution or serum, and providing for 

 the return of the blood to the animal's 

 body by another cannula attached to a vein. 

 The tubes and cannulte are filled completely 

 before attachment with a saline solution 

 which approximates in composition to the 

 salt content of the serum of the animal. 

 This is displaced into the body by the in- 

 flow of blood, when the circulation in the 

 apparatus is established. The blood leav- 

 ing the artery flows through a perfectly 

 closed system and returns to the body 

 within a minute or two without having been 

 exposed to contact with the air or any 

 chance of microbial infection, while the 

 diffusible substances which it contains can 

 pass out, more or less rapidly, through the 

 walls of the tubes. Coagulation of the 

 blood is prevented by injection of hirudin. 

 "We have named the process vividiffusion 

 and the apparatus itself constitutes an 

 "artificial kidney," as it were, but differs 

 from the natural organ in that it makes no 

 distinction whatever between the various 

 diffusible constituents of the blood, per- 

 mitting their escape from the celloidin tubes 



in a manner which is presumably propor- 

 tional to their coefficients of diffusion. As 

 you are well aware, the natural kidney does 

 not ordinarily allow the sugar of the blood 

 to escape into the urine, its excretory func- 

 tion is elective and discriminatory. The 

 artificial kidney, as just stated, makes no 

 such distinction. Sugar is eliminated in 

 proportion to its presence in the blood 

 equally with a waste product like urea. 

 We have it in our power, however, to give 

 to this vividiffusion apparatus a certain 

 selective ability, at least in the sense that 

 we can prevent any given substances, as 

 sugar, glyeocoll, and the like, from escap- 

 ing from the blood, by the simple expedient 

 of placing an equivalent quantity on the 

 outer side of the celloidin tubes. 



With this apparatus we have already 

 separated from the blood a number of con- 

 stituents which can not be obtained with 

 equal ease by other methods. I shall not 

 here enter into the details of the chemical 

 methods employed in differentiating the 

 various constituents of the dialysate, but 

 will merely point out some of the results 

 that we have obtained." It has been 

 found: 



1. That the non-protein constituents of 

 the blood can be accumulated in any de- 

 sired quantity by our method, the quantity 

 depending on the extent of the dialyzing 

 surface of our apparatus and the number of 

 experiments made. 



2. That the rate of accumulation of vari- 

 ous nitrogenous substances in the dialysate 

 and their relative proportions in it do not 

 differ very greatly from those in the blood. 



3. That alanine and valine can be ob- 

 tained in crystalline form; that histidine 

 and creatinine can be shown by reactions 

 to be present. 



4. Quite recently it has been found by 



16 See Jour, of Pharmacology and Experimental 

 Therapeutics, Vol. V., pp. 275-317 and 625-44. 



