82 SCIENCE * PROGRESS 
estimate no absorption took place. Of course, as Salaskin' 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,? and later Langstein,? 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, 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,> 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 (/c.) 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 
Salaskin, Zett. f. physiol. Chem. 35, 1902, 419. 
Embden and Knoop, Hofmeisters Beitrage, 3, 1902, 120. 
3 Langstein, Hlofmeister’s Beitrage, 3, 1902, 373. 
* Abderhalden and Oppenheimer, Zezt. f. physiol. Chent. 42, 1904, 153. 
5 Howell, Amer. Jour. of Physiol. 17, 1906, 273. 
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