The Influence of Samuel W. Johnson on the Chemistry of Proteins *

Samuel W. Johnson, professor of Agricultural Chemistry in Yale University from 1856 to 1896, was the guiding spirit in the establishment of agricultural experiment stations in America. He was the director of the Connecticut Station from 1877 until his retirement in 1900, and was the outstanding agricultural chemist of this country throughout the latter half of the past century. His name is still connected with certain forms of chemical apparatus, especially with apparatus used in determining nitrogen by the Kjeldahl procedure and with a very simple ether extraction device; it is generally conceded that the chemical control of the composition of fertilizers, one of the primary functions of all experiment stations, is largely his handiwork; and the fundamental principles of the policy of experiment stations in their relationship to the public and especially to the farmer were laid down by him. Of his influence as a writer and teacher much has been written, and his lectures, and particularly his articles in the daily and weekly press, were and are still regarded as among the best examples of the popular exposition of agricultural themes. Johnson is not, however, usually considered to have been a protein chemist; and, in fact, he did not at any time contribute by personal experimentation to the subject. Nevertheless, a strong case can be made for the view that Johnson exerted a very powerful influence on protein chemistry in this country. Let us consider first his educational background. In 1853, after a period of study under J. P. Norton at Yale, he went to Germany. He first spent a year under Erdmann at Leipzig where he worked chiefly on inorganic analysis; he then studied organic chemistry for a year with Liebig at the newly established laboratory in Munich. His interest in agriculture led him, however, to read voluminously in the current German literature, to write numerous articles on agricultural topics for the Country Gentleman, and, most interesting and significant of all, to visit the experiment station at Mockern, a village