Unfortunately the absorption in his work proved too much for his health. He was seized by a series of apoplectic attacks which for a time threatened to put an end to his invaluable career. When he did begin to recover his health one of the most serious problems in his regard was to keep him from hindering his convalescence by a return to his old-time absorption in the important problems of the cure and the prevention of disease, at which he had been so happily engaged. The keynote of Pasteur's life was to prevent human suffering as far as possible, and any time not given to this important duty seemed to him to be utterly wasted. With regard to this unfortunate break in Pasteur's work Dr. Christian Herter, in his address on the "Influence of Pasteur in Medical Science," delivered before the Medical Society of Johns Hopkins University, [Footnote 15] has an interesting passage, in which he discusses the significance of the master's work up to this time, and the interest that his illness awakened among all the distinguished medical scientists of Europe at the time: [Footnote 15: New York: Dodd, Mead & Co., 1904.] "It is likely that excessive work and mental stress in some degree contributed to the onset of the series of paralytic seizures which in October, 1868, threatened the life of Louis Pasteur. During the critical period of his illness, many of the most distinguished scientific men of France vied with each other to share with Mme. Pasteur the privilege of nursing the man they loved so well and of rescuing the life {312} that had already placed science and a nation under enduring obligation through discoveries which were either of the greatest practical utility or appeared susceptible of almost unlimited development. Had Pasteur died in 1868, he would have left a name immortal in the annals of science. Others would in some degree have developed his ideas. Already inspired by the researches on fermentation, Lister would have continued to develop those life-saving surgical methods which will forever be associated with his name. But we may well question whether investigations in biology and medicine would not have been for a time at least conducted along less fruitful paths. Who shall say how soon the great principle of experimental immunity to pathogenic bacteria, the central jewel in the diadem of Pasteur's achievements, would have been brought to light?"