104 



Scientific Proceedings (8i). 



In several cases the anterior limbs budded out and differ- 

 entiated in a normal manner, showing all the digits completely 

 formed; such larvae would swim about in a lively manner when 

 they were stimulated. In fact the posterior pieces of these em- 

 bryos developed much beyond the stage at which normal lavree 

 begin to take food, but whether lack of food precluded them from 

 developing farther cannot as yet be stated. 



A definite circulatory system is not necessary for the develop- 

 ment of legs, gill filaments, the growth of the tail or the differentia- 

 tion of internal organs up to quite a late period of larval life. 

 The absence of the thyroid, thymus and pituitary body seems to 

 produce no marked changes up to the period in which the legs and 

 gills are well developed. 



65 (1243) 

 On " racemized " casein. 1 



By Carl L. A. Schmidt. 



[From the Rudolph Spreckels Physiological Laboratory and the Hearst 

 Laboratory of Pathology and Bacteriology of the University 

 of California.] 



The remarkable observation made by Dakin and Dudley 2 that 

 "racemized" casein is not attacked by pepsin, trypsin, or erepsin, 

 is apparently excreted unchanged when injected subcutaneously 

 or given by mouth to a dog, and is unaffected by bacteria, would 

 indicate that the chemical structure of casein had been decidedly 

 altered during the process of "racemization." Dakin 3 suggests 

 that the process is a tautomeric change of the keto-enol type in 

 the manner > CH— CO— NH— ^ > C = C— OH— NH— and 

 that in the case of "racemized" casein this change must be com- 

 plete for all the groups in the protein molecule, otherwise a point 

 of attack for enzymes would be afforded and a partial splitting 

 might occur. If the ketol-enol conversion be complete, the ap- 

 parent discrepancy pointed out by Kober that all racemic peptides 

 are attacked by erepsin would not necessarily be a real one, since 



1 Aided by a grant from the George Williams Hooper Foundation for Medical 

 Research. 



2 Dakin, H. D. and Dudley, H. W., J. Biol. Chem., 1013, 15, 271. 



3 Dakin, H. D. t J. Biol. Chem., 1912-1913, 13, 357. 



