82 SCIENCE PROGRESS 



estimate no absorption took place. Of course, as Salaskin x and 

 Cohnheim himself have shown, there is a small quantity always 

 to be found free in the lumen of the gut. 



Very contradictory statements exist as to whether albumoses 

 and peptones are ever normally present in the blood. One 

 had come to believe that there was no evidence of their presence 

 in this fluid, but a year or two ago definite statements that 

 albumoses had been detected were published by well-known 

 workers. The results were not always positive, however, even 

 with blood examined during the absorption of proteins. Embden 

 and Knoop, 2 and later Langstein, 3 stated definitely that they 

 had managed to prove that albumoses were among the normal 

 constituents of normal blood. This statement has been denied 

 by Abderhalden and Oppenheimer, 4 these workers maintaining 

 that it is not a normal constituent even under the most favour- 

 able conditions. For instance, three dogs which had been 

 starved for several days were given a full meat meal, and then, 

 six to eight hours later, were killed. On examination no trace 

 of a biuret-giving substance was found in the blood thoroughly 

 freed from its protein. They suggest that the positive results 

 have been probably due to traces of protein left owing to 

 imperfect coagulation. Howell, 5 in a recent paper, came to 

 the same conclusion after having carried out many experiments 

 with a fairly large series of animals at different periods of 

 digestion. The method he employed was one of dialysis 

 through membranes permeable to albumoses and peptones, but 

 not to the serum proteins. 



If the absorption takes place in the form of the amino 

 acids, which are soluble bodies, one would expect on examina- 

 tion of the blood to find, after a full protein meal, a very 

 definite increase in the amount of non-precipitable or soluble 

 nitrogen. This, however, does not turn out to be the case, 

 as Dr. Leathes and the writer (I.e.) have shown that there is 

 an increase, but it is not very great. Of course, when one 

 considers the rapidity of the blood flow through the intestinal 

 vessels, it is perhaps rather to be wondered at that any evidence 



1 Salaskin, Zeit. f. physiol. Chem. 35, 1902, 419. 



2 Embden and Knoop, Hofmeister's Beitriige, 3, 1902, 120. 



3 Langstein, Hofmeister's Beitriige, 3, 1902, y]^. 



4 Abderhalden and Oppenheimer, Zeit. f. physiol. Chem. 42, 1904, 153. 



5 Howell, Amer. Jour, of Physiol. 17, 1906, 273. 



