to its outbreak in concrete cases, which may be designated as local, temporal, and that of the individual disposition. What we call the locality must have the infectious matter concealed within itself before persons abiding there are affected. Not every time is alike favorable to the infection; and, when place and time concur, only those persons are affected who offer a suitable personal disposition to the poison. Such persons, even in the worst cases, form hardly five per cent of the population. Thus, the spread of cholera is found to be governed by three factors, the operation of which can be comprehended by all. Further, Dr. Pettenkofer has taught that the danger of attack with cholera does not ordinarily come from persons who are sick, but primarily from the place, showing that the physicians are no more liable than others, and greatly relieving the duty of caring for the sick of its most formidable terrors. The rules respecting disinfection, the discovery of a term, not longer than fourteen days, to which the prevalence of cholera in a particular house is limited, and the prescription of the measures which every one should adopt in the matters of food and drink, clothing and cleanliness, are points of great value for the saving of lives, in which, says Dr. Stieler, Dr. Pettenkofer's determinations have been most definite. If any one makes the objection that these rules contain nothing particularly new, the answer is returned that modern medicine no longer deals in mysterious receipts, but is associated with the nearest and most diversified elements in our life, which not every one knows how to satisfy, or which are neglected because they are commonplace, every-day affairs. It appears now to be the chief purpose of hygiene to convince the masses that the commonest matters are the most important. No science can be less aristocratic, none has to be more intent on popularizing its results. In this popular spirit Dr. Pettenkofer prepared his treatises on "What we can do against the Cholera," and "The Present Condition of the Question of the Cholera." He was president of a cholera commission which met in Berlin at his suggestion, and was a member of the congress which met at Weimar in 1867, with similar objects. His investigations on the cholera, which were afterward extended to typhus and to the various sources of disease in the ground, the air, and the water, have given the impulse to the most comprehensive researches by hosts of inquirers. He constructed an apparatus for exact investigations in respiration, and undertook, in connection with Voit, a series of comprehensive labors on the respiration and nourishment of men and animals, through which many data were collected having an important bearing on the theory of metamorphoses of matter.
Dr. Pettenkofer's works have been published for the most part in professional journals. Since 1842 he has contributed numerous articles in chemistry and kindred subjects to "Büchner's Repertorium," "Dinger's Journal," and the "Denkschrift" of the Munich Academy of Sci-
