His benevolence was most active and never insipid, though marked by an almost feminine sensibility. He was an incomparable companion and friend, and had the gift of smoothing difficulties and inspiring courage, security, and confidence. He took the greatest interest in others and easily came down to their level, always finding points in common, "an opportunity for the study of human documents," he said. Thus he conversed simply and sympathetically with the humble as with the great, with the young as with the old. It was no mere intellectual interest that he bore them, but he put his whole heart into it, which made him extremely easy to approach. And yet he never departed from absolute freedom of speech, sometimes mixed with harshness. Truth and sincerity, for him, came above everything; he carried the courage of his opinions to the highest degree, even if it was likely to shock his hearers or to do him harm. He jealously guarded his independence and nothing could force him to act against his convictions. Full of enthusiasm, always interesting, he enlivened all around him. His ideas and his activity were in constant effervescence; no serious question left him indifferent; he read everything, knew about almost everything, and willingly informed others; his vibrating expansiveness made him a centre of attraction in his private life as in the laboratory or in any other sphere of activity.
From 1873 to 1882 his energies were chiefly absorbed by teaching and by the inner life of the University of Odessa, into which he threw himself with his usual enthusiasm. His lectures were full of life, always bringing out general ideas to throw light upon the most arid facts; he made use of these as an architect utilises coarse materials in order to erect a harmonious edifice. His creative power endowed his lectures with an æsthetic character in spite of their extreme simplicity; not that he concerned himself much about form, but because of his wealth of ideas and the logical way in which he developed them, starting from the simple and reaching the complex in a harmonious synthesis. His own enthusiasm established a living bond between him and his audience.
He was on excellent terms with the students, though he made no bid for popularity. Not only did he give no encouragement to the prevailing tendency of the young men towards politics, but he endeavoured on the contrary to bring them back to their studies; he tried to prove to them that social problems demand knowledge and a serious practical preparation. Otherwise, said he, social life would be as medicine was before it entered into the path of science, and when any middle-aged woman, any bone-setter, was allowed to practise therapeutics. At the same time, students found in him willing protection in the persecutions directed against them, and earnest help in their work when they showed the least interest in it; he would eagerly welcome the smallest spark of the "sacred fire."