The bearing of these researches of Pasteur on vaccination with cow-pox, and the whole of the Jennerian doctrines, will be evident. They throw a flood of light both on the efficacy of vaccination and the many supposed failures which have given a handle to the unscrupulous fanatical detractors of Jenner and his doctrines. They go far toward establishing the correctness of the view entertained by Jenner as to the identity of small-pox and cow-pox, showing how great may be the modifications effected in the original virus by repeated transmission, either through the animal or the human system.
But apart from the question of identity or diversity of small-pox and vaccinia, Pasteur's researches prove beyond all question that a disease virus may be both diminished and augmented in power by physiological devices, and that therefore the efficacy of the vaccine lymph may, in various ways, be so diminished as to lose its protective power, without shaking our faith in the principle of vaccination or detracting in the least from the inestimable value of Jenner's discovery. The attention of the scientific world will now be, and is, directed to the important inquiry, How far has the original vaccinia of Jenner lost its protective power? If so, how has this been brought about, and by what means can it be restored? Must we again revert to the cow for a new supply? Need we only be more scrupulous in the selection of the vesicles, and the particular stage of their development, and in the mode in which the operation of vaccination is performed? These and numerous other similar questions are now being discussed and investigated, but none probably is more important than the question how far the protective influence in each individual is dissipated by time, and hence the principle of re-vaccination is now being enforced. There can be no doubt that different epidemics possess different degrees of virulence, and what proves a sufficient protection in a mild epidemic of small-pox may not be sufficient in a more virulent one. In certain seasons and in certain conditions of the atmosphere, the human system is more prone to certain disease than at other times. Pasteur's experiments on cultivated virus or germs show that in the course of time, and in certain conditions of exposure to the action of oxygen or other agents, the vitality, or constitution, so to speak, of the germs may be so changed as materially to alter their action on the animal system. We have, therefore, scientific grounds for reverting from time to time to the heifer for a new stock, rather than continuing to rely on the perpetual transmission from one human body to another.
This is not the place to enter on the whole question of the germ theory of disease, but who does not see how wide is the field for investigation opened up by Pasteur and others? Already the application of the principle of vaccination has been successfully applied by Pasteur to a very fatal epidemic disease attacking fowls, and known by the name of “chicken cholera.” By inoculating chickens with the cultivated variety of the particular “bacillus” he has afforded to them complete protection. The economic value of this to France may in some measure be estimated by the many millions of eggs which are exported from France to this country alone. How many other diseases, such as scarlatina and diphtheria, which now carry off annually thousands of children, may not ere long be extinguished by like means who shall say? “I venture,” states Mr. Simon, in his address to the Health Section of the International Congress, “to say that in the records of human industry it would be impossible to point to work of more promise to the world than these various contributions to the knowledge of disease and of its cure and prevention, and they are contributions which, from the nature of the case, have come, and could only have come, from the performance of experiments on living animals.”
Compulsory vaccination is, no doubt, a strong measure, and one which might, in this land of individual liberty, be expected to give rise both to question and opposition. It can only be justified by proving that it is to the interest of the individual as well as of the whole community that it should be enforced. Of its propriety and necessity we believe it needs only a calm and unprejudiced inquiry to be convinced. Most of the objections raised against it are either baseless or admit of being obviated. That some of the objections are of a character that command our respect may be admitted, but mere sentiment or prejudiced and ill-founded objections, must give place to sound arguments and well-established evidence. In this, as in many similar cases, opposition and discussion open up entrances for light by which the clouds of ignorance and darkness are sure to be dispelled. But even as this whole question of vaccination now stands, the responsibility of those who are persistently misrepresenting facts and misleading the public is great, nay, criminal, when we reflect how many lives are sacrificed by the neglect of precautionary means within the reach of all.
LOUIS PASTEUR AND HIS WORK
Patrick Geddes and J. Arthur Thomson
[Professor Geddes is Professor of Botany at University College, Dundee. He has written “Chapters in Modern Botany” and many botanical articles and papers. Professor Thomson is Regius Professor of Natural History, Aberdeen University. His works include “The Study of Animal Life,” “Outlines of Zoölogy,” “The Natural History of the Year” and “The Science of Life.” “The Evolution of Sex” was written jointly by both these authors. The article from which extracts follow was published in the Contemporary Review, 1895: the editor's permission to reprint is gratefully acknowledged. The Life of Louis Pasteur by M. Radot, 2 vols., were published by McClure, Phillips & Co., New York, 1901.]
The course of Pasteur's scientific work is one of remarkably natural and logical sequence. As the veteran M. Chevreuil long ago said in the Academy of Sciences, “It is by first examining in their chronological order the researches of M. Pasteur, and then considering them as a whole, that we appreciate the rigor of his conclusions, and the perspicacity of a mind which, strong in the truths which it has already discovered, sweeps forward to the establishment of what is new.” We shall therefore summarize the record of his greatest achievements.