ESMOND E. SNELL 



TABLE I 

 Progress in Recognition of Vitamins and Growth Factors, 1942-1955 



I. Substances known to serve as vitamins for both animals and microor- 

 ganisms. 



A. Pyridoxal and pyridoxamine 



1. Bioassay organisms used in detection: Streptococcus faecalis 

 {lactis) R: Snell, Guirard, and Williams, 1942 (73) 



2. Characterization and synthesis: Snell, 1944 (62); Harris, 

 Heyl, and Folkers, 1944 (20) 



B. Folic acid (pteroylglutamic acid) and its conjugates 



1. Bioassay organisms used in isolation and characterization: 

 Lactobacillus casei: Snell and Peterson, 1939, 1940 (69) 

 Streptococcus faecalis: Mitchell, Snell, and Williams, 1941 (37) 

 Chicks: Hogan and Parrott, 1939 (23) 



2. Isolation 



Pfiffner, Binkley, Bloom, Brown, Bird, Emmett, Hogan, and 



O'Dell, 1943 (45) 



Hutchings, Stokstad, Bohonos, and Slobodkin, 1944 (26) 



3. Characterization and synthesis 

 Angier and co-workers, 1946 (1) 



C. Folinic acid (leucovorin) and its conjugates. 



1. Bioassay organisms used in isolation and characterization: 

 Leuconostoc citrovorum: Sauberlich and Baumann, 1948 (56) 

 Streptococcus faecalis and Lactobacillus casei: Bond, Bardos, Sibley, 

 and Shive, 1949 (4) 



2. Characterization and synthesis 



Pohland, Flynn, Jones, and Shive, 1951 (47) 



Cosulich, Roth, Smith, Hultquist, and Parker, 1952 (11) 



3. Isolation 



Kcresztesy and Silverman, 1951 (27) 



D. Pantetheine — Pantethine 



1 . Bioassay organism used in detection : 



Lactobacillus bulgaricus: Williams, Hofr-J0rgensen, and Snell, 

 1949 (82) 



2. Purification and characterization 



Peters, Brown, Williams, and Snell, 1953 C41) 

 Brown, Craig, and Snell, 1950, 1953 (8) 



3. Synthesis 



Snell, Brown, Peters, Craig, Wittle, Moore, McGlohon, and 

 Bird, 1950 (72) 



90 



