84 SCIENCE PROGRESS 
the methods of analysis employed it was not detected. On 
the other hand, these amino acids can lose their nitrogen fairly 
readily through the action of the body tissues, as has been 
demonstrated by the work of Jacoby! and of Lang.? Lang 
showed that if one mix various amino acids with chopped-up 
animal tissue, such as liver, spleen, intestine, etc., the amino 
groups are split off. For instance, glycocoll was found to give 
up its nitrogen freely when mixed with liver, but even more 
freely when in contact with intestinal tissue. Tyrosin could 
be attacked by the liver, but only with difficulty. Leucin, on 
the other hand, was fairly readily decomposed by that organ, 
and so on with other amino acids. Thus it may be that the 
absorption of the decomposition products is in the form of 
bodies nitrogen free, as acids of the fatty acid series such as 
lactic acid. In favour of this view, perhaps, the work of Nencki 
and his co-workers may be cited. Nencki, Pawlow, and 
Zaleski* showed that the blood taken from the portal system 
contains three to four times more ammonia than the systemic 
arterial blood. This is extremely well marked where the 
animal has previously been fed on a meat diet. This ammonia 
might be regarded as that split off from the amino acids during 
or after their course through the intestinal wall, and which, 
for the most part, is being hurried to the liver, there to be 
converted into urea for excretion. It must be remembered, 
however, that according to Horodynski, Salaskin, and Zaleski 4 
starvation has practically no effect on the amount of ammonia 
in the arterial blood, and that there is only a very slight 
reduction in the amount present in the portal blood. 
Others, again, hold that there is no such simple absorption, 
but that as soon as they are absorbed the products of digestion 
undergo synthesis, and in this reperfected form reach the body 
circulation. As regards this question of regeneration of a 
coagulable protein, Dr. Leathes and the writer (/c.) were quite 
unable to detect any such increase, although this question was 
carefully gone into. Neither by an estimation of the total 
nitrogen before and after absorption nor by controls carried 
out by observations on the amount of haemoglobin, were we 
1 Jacoby, Zeit. f. physiol. Chem, 30, 1900, 149. 
? Lang, Hofmeisters Bettrage, 5, 1904, 321. 
® Nencki, Pawlow, and Zaleski, Schmiedeberg’s Archiv, 37, 1896, 26. 
4 Horodynski, Salaskin, and Zaleski, Zezt. f. physiol. Chem. 35, 1902, 246. 
