RT Journal A1 Terry MC T1 ARtificial concentration of test serums in blood grouping JF Journal of the American Medical Association JO Journal of the American Medical Association YR 1939 FD January 14 VO 112 IS 2 SP 135 OP 136 DO 10.1001/jama.1939.62800020002008b UL http://dx.doi.org/10.1001/jama.1939.62800020002008b AB In a recent issue of The Journal Hoxworth and Mahoney1 call attention to the importance of using only test serums of high agglutinin titer in the determination of blood groups and report their success in concentrating inferior serums by the lyophile process to a titer considerably higher than that proposed by Coca2 for a first grade reagent for this purpose.Occasionally, as has been Hoxworth and Mahoney's good fortune, serums will be found which equal or exceed the requirements for Coca's grade I, but most of them fall below that standard, and methods for raising the titer of low grade serum are, as Hoxworth and Mahoney say, highly desirable.The method of concentration by alternate freezing and thawing,3 to which Hoxworth and Mahoney refer, was originally employed by O'Meara,4 a fact not known to me at the time I made the report; due acknowledgment of O'Meara's