ABSORPTION OF PROTEIDS. 439 



Changes in albumose and peptone during absorption. 1 Although 

 there is no doubt that a considerable, if not the greater part of 

 the proteid of the food is absorbed as albumose or peptone, these 

 bodies are never found in appreciable amount in the blood. Schmidt- 

 Mlilheim 2 stated that the maximum amount in serum is 0*028 per cent.; 

 but recent experiments by Neumeister 3 have given an altogether 

 negative result, and, according to this observer, albumoses are not present 

 at all in blood, even in traces. 



Injected directly into the blood, albumoses and peptone are treated 

 by the organism as foreign bodies ; they are not assimilable proteids, but 

 are promptly excreted by the kidneys, unless injected in large quantities, 4 

 and in a short time practically all the peptone and albumose injected is 

 found in the urine, while not a trace is to be found in the blood. 5 

 That albumose and peptone are foreign substances in the blood stream, 

 is shown not only by this rapid elimination, but by the fact that they 

 possess, besides, marked toxic properties, and cause the death of the 

 animal when injected in larger doses, producing an immense and rapid 

 fall in arterial blood pressure ; in addition, they so alter the nature 

 of the blood that on drawing it from the vessels it no longer coagulates, 

 or does so very slowly. These results, taken in conjunction with the 

 fact that normal urine never contains albumoses, even in traces, prove 

 that the albumoses and peptones absorbed from the alimentary canal 

 never reach the general circulation as such, but are somewhere on their 

 route converted into other substances which can harmlessly enter the 

 circulation. Positive experiments on the subject not only confirm this 

 indirect proof, but clearly indicate that the change takes place in the 

 lining epithelial cells. 



Seat of the modification of albumose and peptone during absorption. 

 It might be supposed that the albumose and peptone disappeared as 

 such in the liver ; this is not, however, the case. Schmidt-Mulheim 6 

 found that the portal vein during proteid digestion contained no greater a 

 percentage of these bodies than the arterial blood, and Neumeister 7 found 

 that the portal vein, while absorption of peptone was going on, did not 

 contain a trace of this material. Neumeister also circulated defibrinated 

 blood, to which peptone had been added through a liver immediately 



1 In many of the papers referred to in this section, "peptone" is used to signify what 

 would to-day be called a mixture of albumose and peptone ; this has usually been trans- 

 lated by albumose and peptone, or by albumose. 



2 Arch.f. Anat. u. PhysioL, Leipzig, 1880, S. 33. See also Hofmeister, Arch. f. exper. 

 Path. u. PharmakoL, Leipzig, 1885, Bd. xix. S. 17. 



3 Ztschr. f. BioL, Miinchen, 1888, Bd. xxiv. S. 277. Neumeister caught the blood 

 from the carotid in ammonium oxalate to prevent clotting ; laked by shaking with ether ; 

 removed ether ; saturated with ammonium sulphate ; filtered ; reduced filtrate by evapor- 

 ating to a small bulk, filtering from time to time from crops of crystals ; and tested in final 

 filtrate for albumoses by the biuret test with negative results. Control experiments showed 

 that even a trace of albumose added to the blood intentionally could be easily identified. 



4 When large amounts are injected, the fall in arterial blood pressure is so great that 

 secretion of urine is arrested. Even in such a case the albumose does not remain in the 

 blood, but passes into the lymph (Shore, Journ. PhysioL, Cambridge and London, 1890, 

 vol. xi. p. 549). 



5 Ploz and Gyergyai, Arch.f. d. ges. PhysioL, Bonn, 1875, Bd. x. S. 536 ; Hofmeister, 

 Ztschr. f. pliysiol. Chem., Strassburg, 1881, Bd. v. S. 131 ; Schmidt-Mitlheim, Arch. f. 

 Anat. u. PhysioL, Leipzig, 1880, S. 33 ; Fano, ibid., 1881, S. 281 ; Shore, Journ. PhysioL, 

 Cambridge and London, 1890, vol. xi. p. 528. A similar effect folloAVS subcutaneous 

 injection (Hofmeister, loc. cit.}. 



6 Arch. f. Anat. u. PhysioL, Leipzig, 1880, S. 33. 



7 SUzungsb. d. phys.-med. Gesellsch. zu IViirzburg, 1889, S. 65; Ztschr. f. BioL, 

 Miinchen, 1888, Bd. vi. S. 287. 



