more." The cackling done, the egg is dropped into the Schizomycetes, and is duly addled. And yet these specialists swell with importance and ruffle their feathers and insist that one ignorant of their technique cannot by any possibility show them how to hatch their eggs.

It appears to me that there is no greater fallacy in minute pathology, or more vulgar error, than is to be found in the supposition that the discoverer of a pathogenic form can make better use of it than anybody else. And there is no more pernicious or apparently more prevalent belief than that facts are valueless in the hands of one who is not prepared to adduce new facts, or to reproduce old facts; unless it be the confident and cherished belief that in bacteriology all possible conclusions have already been drawn from all known facts, and that, consequently, nothing is to be learnt from new readings of old facts. However, the notion which is now in vogue and is rigidly upheld that no man shall be supposed to be capable of thinking out an etiological problem unless he shall first cultivate the microbe concerned in it-will not last for ever. The absurdity of such a notion has been recognised in other departments of science, and it cannot be held on to much longer in etiology.

In Professor Newton's address to the biological section of the British Association at Manchester on the 1st of September last he said: "I have for a long while maintained that, as a matter of fact, what is now known as the Darwinian theory did not, except in one small point, require a naturalist-and much less naturalists of such eminence as Mr. Darwin and Mr. Wallaceto think it out and establish its truth. Pray do not for a moment. imagine that I wish to detract from the value of their demonstration of a discovery that is almost unrivalled in its importance when I say, that the demonstration might have been perfectly well made by any reflective person who was aided by that small amount of information as to the condition of things around him which is presumably possessed by everybody of common sense. It might have been perfectly well made by any of the sages of antiquity. It might have been as well made. by any reasoning man of modern time, even though he were

innocent of the merest rudiments of zoology or botany; and, as is admitted, the discovery was partly, and almost unconsciously, made by Dr. Wells in 1813, and again by Mr. Patrick Mayhew in 1831, neither of whom pretended to any special knowledge of those branches of science." 1

Whether the explanation to be offered here of the cause, or causes, of measles shall satisfy the judgment of etiologists is doubtful, and whether it shall even get a hearing in the courts, as at present constituted, I know not. Possibly the great authorities may not be able to shed their skins of contempt for those who, though not adepts in research, try to utilise the facts already brought out; and they may elect to continue to look on placidly while facts on facts are piled up and left to future generations. If they persist in discarding all inferential, or "speculative," etiology as unprofitable, of course the soundness or otherwise of conclusions will not influence their minds; yet I venture to affirm that to those who dare draw an inference it will be evident that there is no escape from some of the most important of the conclusions here submitted, both in regard to the causation and to the prevention of measles. It may not be possible to prove them to demonstration for some time to come, but the data extant are so weighty, significant, and numerous, that, collectively, they amount to presumptive proof of the highest order; and I cannot but marvel that the plain deductions from phenomena that are constantly recurring should have been missed for so long. If indeed it be held, as Professor Newton has propounded, that "what is now known as the Darwinian theory" has been demonstrated, the cause of measles. admits of demonstration with infinitely greater facility. And, moreover, to borrow Professor Newton's words, "I say that the demonstration might have been perfectly well made by any reflective person who was aided by that small amount of information as to the condition of things around him which is presumably possessed by everybody of common sense."

Perhaps the demonstration could not have "been perfectly well made by any of the sages of antiquity;" but if a sage, guided

1 The Times, September 2, 1887.

by pure accident or keen observation, had been led to reflect upon or had been moved to examine into the conditions which precede the disease, and if he had brought out the conditions which are constantly present when it occurs, and without which it does not occur and he might easily have done this, if his attention had been specially drawn to the one cardinal pointhe might have arrived at such conclusions as would have enabled the ancients to have prevented measles with absolute certainty, with little trouble, and at a trifling outlay. But setting aside. the ancients, the demonstration of the cause of measles certainly 'might have been as well made by any reasoning man of modern times, even though he were innocent of the merest rudiments" of medicine or micro-pathology. This, I think, will be admitted when the simple nature of the ratiocination required to connect the primary cause or causes of the disease with its occurrence shall be perceived.

The nature of the work in this field, however, would seem to have induced a singular and an anomalous state of things in regard to what is to be deemed sufficient proof. In pure pathology no proof is admissible but the experimental. The micro-pathologist proper has laid down laws of the severest kind for his own research, and insists upon their most rigid observance in the case of every pathophyte or assumed pathophyte. Analogy is thrown over as altogether unsafe, and the observations made in one investigation in the case of one pathophyte must be repeated in every other investigation in the case of every other pathophyte, under pain of having otherwise most excellent work cast aside as incomplete or defective, and therefore inconclusive and temporarily worthless. Every step, hedged round with every precaution, taken in one case, must be taken surrounded with all the like precautions in all like cases. In short, some of the requirements considered essential to getting at the truth in this description of inquiry are slightly vexatious. But we need not stay to object to the waste of time involved in repetitions designed to make assurance doubly sure. A punctilious adherence even to arbitrary laws is generally, at all events, a fault on the right side. Yet bearing in mind his ex

B

eessive scrupulousness in this direction, it is startling to find that, when the pathologist comes to look at the botanical aspect of a pathophyte, he at once throws away all method and becomes the wildest of speculators. Although so exacting in the matter of experimental proof on his own side of the inquiry, he boldly invades the domain of the botanist and, giving a loose rein to inference, rides rough-shod over the nicest questions. No longer held in by the hard and fast lines of pathological research, he now unhesitatingly accepts uncertain assumption as complete demonstration. He takes up one view of an open and long dis- . puted question in mycology, and without looking or caring for experimental proof, adopts it incontinently, and forthwith systematises on it, as though it were firmly established truth.

This abandonment, or reversal rather, of the canons enforced in the pathological branch of etiological inquiry, when the venue is changed to the botanical branch, is perplexing. It is incomprehensible why the pathologist, after following his special research with such deliberate and cautious steps, should suddenly turn round and take an opposite and reckless course just at the very point where it is all-important to move warily. For if there is one thing in botany more uncertain than another, it is the true position of the pathophytes. There is no question at the present moment in the whole province of etiology which more urgently demands to be set at rest by competent botanists, than the question whether any one or all of the specific vegetal forms that have been demonstrated, or have been inferred, to be the infective agents in the diseases with which they have been severally connected, are species, or merely stages in the cycle of species. This is by far the largest and most important question still pressing for determination in botany. Pathologists long ago adopted the assumption, and have hitherto adhered to it, that the pathophyte is an independent species, notwithstanding that it could not, admittedly, be determined; and until it is definitely settled, and it may take another twenty-five years to settle it, many dependent questions as to the vegetation will in effect be suspended, even though they

are now supposed in the bacteriological world to have been completely and finally disposed of.

The point here, however, is the inconsistency of the pathologist in leaving experimental proof behind him in pathology and contenting himself with inferential processes in botany; as though a higher form of proof were demanded in the one subject than in the other. It will be understood too that exception is not taken to the fact that the pathologist should utilise inference. That is the last objection that would be taken here. But what appears inconsistent is, that whilst he rejects everything in the shape of reasoning from pathological facts, he should consider himself quite within scientific rules in forming or accepting conclusions of the utmost importance upon the scantiest of botanical data. And what appears almost as inconsistent is that by a tacit understanding his inconsistency shall be overlooked, and he shall be allowed and entitled to form hypotheses at will upon botanical and other evidence; and that that which in the inquirer who elects to take his data from more skilled hands, and to look by the aid of more educated eyes than his own, is rank speculation, is in the pathologist authoritative utterance.

The micro-etiologists, or dilettanti pathologists, who dabble in what is euphemistically called research, and who follow in the wake of the greater pathologists, and reproduce their experiments, have echoed and re-echoed their dicta. For them the only safe or legitimate sources of evidence touching infective disease are the observations made in certain laboratories, and the botanical facts stored in bacteriology, with perhaps a few clinical and other data that seem to tell for particular theories, and have, consequently, been employed and thereby sanctioned (data telling the other way being excluded) by the higher order of pathologists. For them old facts have been sucked dry and have no more meaning, everyday phenomena have no more significance than has already been apprehended, and new facts cannot be received unless stamped by authority. In short it is virtually ordered, not only that all our knowledge of infective material and of infective processes must come from a