In one instance, where recovery was not aimed at, a dog anesthetized 

 with chloretone was kept alive during a dialyzing period of sixteen 

 hours with about one-third of its blood outside the body. At the end 

 of an experiment the larger proportion of the blood in the apparatus 

 may be driven back into the body by air-pressure or by means of a 

 saline solution which is allowed to flow into the dialyzing tubes from 

 a higher level and which thus drives the blood ahead of it into the 

 body. 



Many experiments have been made to determine the best form of 

 apparatus combining maximum diffusing surface with minimum vol- 

 ume, absolute freedom from leaks, ease of construction, uniformity of 

 flow, minimum exposures to surfaces of glass or other substance liable 

 to favor clotting, etc. The most efficient type in use at present has 

 thirty-two celloidin tubes of 8 mm. diameter, 40 cm, long, fastened 

 by tying with a string to a system of glass tubes branching dichoto- 

 mously, so that the flow of blood takes place horizontally twice in 

 each direction through eight tubes in parallel. (An apparatus of this 

 size can only be attached to animals of at least fifty pounds' weight.) 

 Flattened tubes and other types are being tried, while very small tubes 

 will undoubtedly prove valuable when the necessary time and trouble 

 are not prohibitive. [See illustration between pages 16 and 17.] 



Such an apparatus can obviously be used in the solution of many 

 problems, both therapeutic and physiological, and is especially valu- 

 able in the latter case because, apart from the necessary anesthetic, 

 the normal physiological condition is in nowise disturbed, as by 

 bleeding to obtain large amounts of blood. Diffusible substances, 

 present in only small proportion at one time, may be isolated in con- 

 siderable quantities provided they are regenerated in the body as fast 

 as they are removed. Evidence of this has already been obtained in the 

 case of the dialyzable (non-proteid) nitrogen which is extracted in 

 large quantities in prolonged experiments. Determinations by Van 

 Slyke's method have shown a high proportion of nitrogen in the form 

 of amino gioups (NHo), and experiments are in progress for the iso- 

 lation of individual amino-acids by Fischer's esterification method. 

 Several grams of the esters have been obtained by distillation in a 

 vacuum of 1 to 16 mm. at temperatures from 70° to 180° C. Bases 

 precipitated by phosphotungstic acid have also been obtained, but 

 they apparently constitute a more complex mixture than those usu- 

 ally obtained in the digestion of proteins by acids, and the discovery 

 of new bodies, possibly including polypeptids, seems probable. 



Quantitative data have been obtained with a view to comparing the 



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