E. V. McCOLLUM Johns Hopkins University, Baltimore, Maryland
other solutions containing alhuminons substances, and found that all of the proteins tested were completely precipitated by saturating their aqueous solutions with ammonium sulfate. He went on to say that the proteins thus precipitated were not changed in their solubility. He employed this method for removal of proteins from milk to secure a solution suitable for determining milk sugar with the saccharimeter. This great contribution was published in August, 1878.5 Kiihne4 in 1885 concluded that when a mixture of the products of tryptic digestion of protein was precipitated with ammonium sulfate, protein was precipitated leaving "peptone" behind, and he suggested this method for the preparation of pure peptone. This started a controversy which contmued over a decade, others believing that both albumoses and peptone were precipitated with protein. Osborne made extensive use of ammonium sulfate precipitation in his classic studies of the proteins of the seeds of plant^.^ Thomas Graham in 1861 discovered that crystalloids passed by diffusion through a semipermeable membrane, whereas such colloids as gelatin and silicic acid did not. This provided later workers with a method for recovering precipitated proteins ohtained by MBhu's method (after filtering they could be freed from residual ammonium sulfate by dialysis). MBhu's discovery led later investigators to try the effect of other salts as protein precipitants. Magnesium and zinc sulfates were found to be especially useful for fractional precipitation of mixtures of proteins. Ammonium sulfate apparently has no equal as a reagent for separating and purifying individual proteins free from electrolytes. That MBhu's conclusion was correct, that proteins so precipitated were unchanged, is supported by a great number of investigations which show that enzymes precipitated by this method still Biographical memoirs of C. J. M. M6hu: retain their specific activity, and that proteins so pre(a) Leopoldina, 23, 218 (December, 1887). (6) MARTY,M., Bull. a d . m a . (Paris), 2nd Ser., T XWI, cipitated from solutions retain their immunologic llS?W> ,A"v.,. specificity.
A u m o R s of monographs on proteins and of comprehensive textbooks of biochemistry do not mention the name of the man who made one of the most important discoveries in the entire history of protein iuvestigations. He was Camille Jean Marie MBhu, who was born a t Auxonne (Cote-d'Or) on March 10, 1835, and died in Paris in 1887. His contribution to the technique of protein research should be brought to the attention of biochemistry students. He began the study of pharmacy a t Dijon, but a t the age of 21 he went to Paris. He was said to have had a$ that time no resources other than a great enthusiasm for work and a determination to make a career for himself in science. He continued his studies in pharmacy and successively occupied positions as pharmacist in several hospitals in Paris. He studied medicine and was made doctor of medicine in 1865.' MBhu had great enthusiasm for applying chemistry to medicine. He devoted much study to the purification of tartrates, citrates, and salts of iron, mercury, and bismuth compounds used in pharmacy. He devised a method for determining the fat content of butter, improved on the sodium hypochlorite method for determining urea in urine, and sought to improve methods for estimating sugar and protein in pathological fluids He wrote a book on medical chemi~try.~ The discovery which placed him among the torchbearers of biochemistry was the outcome of his efforts to separate the pigments from a sample of pathologic urine. By a happy inspiration he tried saturating the urine with ammonium sulfate and found that the pigments were precipitated. He followed up this observation and found that bile acids, much, and bile pigments were precipitated by saturation with this salt. He then applied his reagent to serous fluid, milk, and
(e) J. phann. chim., 5th Ser., 16, 574 (1887). (d) "Le Centenaire du Journal de Pharmacie et de Chimie: 1809-1909. Historie du Journal et Notices Biographiques par Emile Bourquelot," Paris, 1910, p. 103. 8 MOHU,C. J. M., "Trait6 Pratique et l%mentaire de Chimie MBdicde, Appliquee aux Recherche8 Cliniques," 2nd ed., Paris, 1878.
"*nu., J. p h m . chim., 4th Ser., 28, 159 (1878). KWHNE, W., Verhandl. Na1urhistor.-med. Vweins zu Heidelberg, N.F. 3, 286 (1885). OSBORNE.T. B., "The Vegetable Proteins," 2nd ed., Longmans, Green and Co., New York, 1924.
