Antagonistic Action of K and Ca upon Na. ii 
beyond the 2 cell stage; while in the alkaline solution all seg- 
mented and reached the 8 or even 16 cell stage. It should be 
added that the eggs of Arbacia will develop in a neutral solution 
of Na+K+Ca to the blastula stage. 
I found also that in mixtures of Na+Mg or Na+Sr or Na+Ba 
more eggs of Arbacia segmented and reached a higher stage of 
segmentation, when the solutions were slightly alkaline than when 
they were neutral. These experiments seem to indicate that for 
the fertilized eggs of the sea urchins the antagonistic action of 
Ca to NaCl makes itself felt mostly in such processes in which a 
concentration of HO ions higher than io~ 7 N is required, while 
the K ions act antagonistically to NaCl through their participation 
in processes which may take place in neutral or even slightly acid 
mediums. 
7 (532) 
Digestion of protein in the stomach and intestine of the dogfish. 
By DONALD D. VAN SLYKE and GEORGE F. WHITE. 
[ From the Laboratories of the Rockefeller Institute for Medical 
Research and the Laboratory of the U. S. Fish 
Commission at Woods Hole.] 
Dogfish were fed by a tube with chopped, coagulated beef, and 
killed after 6, 12, 24, 48 and 72 hours. In the contents of the 
intestine and stomach determinations were made of (a) insoluble 
nitrogen, (b) soluble nitrogen, (c) soluble nitrogen in amino form, 1 
and (d) soluble nitrogen in amino form after complete hydrolysis. 
The ratio d : c indicates the average size of the peptides composing 
the peptone mixture. 
During the first six hours about one half the ingested protein is 
dissolved and one fourth absorbed. The unabsorbed peptones 
are, on the average, of pentapeptid complexity. Very little 
transfer of stomach contents to the intestine occurs. 
At the end of 12 hours 30-45 per cent, of the protein in the tract, 
including both solid and dissolved matter, is found in the intestine. 
The peptone in the stomach is broken down to the tripeptid 
stage, that in the intestine slightly farther. 
^an Slyke, these Proceedings. 
