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As a general proposition it may be maintained that, although there are many occasions when systematic attack with de- structive appliances is advisable, and several instances where it has been eminently successful the Herculean cleansing of the yellow-fever and malaria stricken Panama Canal Zone from infective mosquitos by Gen. Gorgas and his staff being the crown and garland of them all yet the only permanently success- ful procedure against a harmful arthropod is to upset its environ- ment by steady perseverance in the ordinary principles of hygiene.

The truth of this proposition is illustrated by the history of malaria in England. Not so very long ago malarial fevers were quite common in many parts of that country: in 1657 John Evelyn's son Richard died at Deptford " after six fits of a quartan ague ": in Shakespeare's time ague must have been an every-day affair, for it is a familiar word in the mouth of his people, from homely persons like Mistress Quickly to great personages like Hotspur and Richard II. : Sir John Falstaff died of a " burning quotidian tertian," old John of Gaunt expired in an ague fit with " frozen admonitions " on his lips, and Sir Andrew Aguecheek is a catch-name for a shivering coward. Yet, except in a few water-logged spots where it may still linger, ague quietly dis- appeared from England ere ever any connexion with Anopheles mosquitos was dreamt of, or ever any malaria parasite had been discovered by a Laveran, although the species of Anopheles that used to spread it in England are still familiar British insects to those who know where to look for them. Anopheles mosquitos prefer to shelter in dark damp habitations, and they do not fly far from the waters where they are bred; and what seems to have happened in England is that, in the general improvement of drainage and sanitation, conditions have changed so completely that the population no longer lives among the breeding-haunts of Anopheles in houses that offer any attraction to those insects, and that thus the old communion between man and Anopheles, by which malaria was fostered, has gradually been dissolved. Something of the same sort has happened in the well-kept European quarters of some of the large towns of India.

It follows that medical entomology is really a branch of hy- giene a branch that finds its fullest application not so much in settled countries where man has long since set a bound to organic nature, as in those vast imperfectly developed tropical territories where sanitary arrangements are crude or non-exist- ent and man is struggling with his organic environment.

As a branch of hygiene medical entomology oiiould also be concerned with questions of the unwitting dissemination of pathogenic arthropoda in the intercourse of trade and travel, and in the special circumstances of war; and also with difficult problems relating to the destruction of such elements of the fauna of a particular territory as are believed to foster some local noxious arthropod, and to the introduction of such exotic species and parasites as are thought likely to destroy some local noxious arthropod, as sanitary measures; for such measures, if lightly undertaken, may start new mischiefs without mitigating those they are intended to check. (A. A.)

MEDICINE AND SURGERY (see 18.41 and 26.125). By the year 1910 medical thought had reached one of its turning points, though this fact was not immediately evident. The great age of bacteriology had so vastly enriched our knowledge of disease that other aspects of work had been somewhat neglected. The belief prevailed that every disease was due to the presence of some microorganism, and that patient effort was bound, sooner or later, to find the specific microorganism in each case and en- able a great work of prevention to be undertaken. In consequence bacteriology attracted the best brains in medicine, and enormous labour was expended in the search for organisms and in the study of their methods of growth. The fruits of this labour look smaller in the retrospect than the hopes concerning them which were entertained. A few new organisms have, it is true, been discovered, for example the spirochaete of infective jaundice (Weil's disease), the so-called filter-passers, and the still rather dubious rickettsia bodies supposed to be associated with typhus fever, trench fever and other conditions. Some differentiation, too, has been made between various "strains" of bacteria,

notably in connexion with cerebro-spinal meningitis and bacillary dysentery (see BACTERIOLOGY). But an impression has gradually arisen and is growing that the greatest conquests in this field belong to the past. The trend of modern ideas is rather towards the application and elaboration of the knowledge newly obtained, and its absorption into the general body of medical thought.

I. GENERAL PROGRESS IN MEDICINE, 1910-21

In any review of recent progress the above considerations must be borne steadily in mind. The mere circumstance that many common diseases for example measles, scarlet fever, rheumatic fever are still unrelated to a specific causative organism is much less significant than the fact that the after-effects of these complaints have been intensively studied and that the applica- tion of the laws of bacteriological invasion and growth has saved many victims who in other days would have perished.

One of the first results of the new orientation was a conception of disease as a process dependent on another parallel process the course of an infection. The human body reacts in variour, ways to various assailants. This reaction is expressed in symp- toms which tell us of the struggle going on, and may enable us, if we understand their mechanism, to arrive at conclusions about the nature of the attacking force and the strength of the defences. The researches of the laboratory are available here as an addi- tional source of enlightenment, and so fall into their place in the general scheme of clinical medicine.

Importance of Prognosis. When the World War broke out in 1914 this was the point which had been reached. Sir James Mackenzie and other thinkers, whose outlook was primarily clinical, were recalling attention to the lack of knowledge of symptoms and the lack of understanding of their importance. Medicine, they declared, was concerned too much with the gross signs of disease, too little with its earlier manifestations. The post-mortem room had too great an influence on opinion, and even the laboratory had failed to perceive that a vast body of truth lay beyond its reach. The positive side of this teachingwas the setting-up of certain functional tests to replace the physical ones then in vogue. It was argued that, no matter what devia- tions from the normal form an organ or system might show, if it remained functionally efficient it could not, on account of such deviations, be condemned out of hand.

T his doctrine was really a challenge. It demanded a restate- ment in the name of prognosis. The physician must be able to interpret symptoms and laboratory findings in terms of life. He must be in a position to tell his patient what a particular sign betokened, how it would affect him, and how its cause might be removed or rendered harmless. In short, the physician must draw upon all the sources of information available, yet must not abrogate his place as interpreter.

The position taken up was assailed from several quarters. But the outbreak of war served almost immediately to reveal its strength. When that event took place the medical profession was called on suddenly to examine a vast number of men and express views as to their fitness for field service. These views were stated with the knowledge that they would be put to the test immediately and that if they were erroneous the fact would soon be discovered. A test of this kind constitutes a great event in medicine. It will certainly be seen in the retrospect as one of the turning-points of the science. For it brought the whole body of knowledge to trial; it brought the exponents of every theory to account. More than this, it revealed the key to the problem of future progress prognosis. The doctor was asked to say what the patient could do; it was not enough merely to recount symptoms or signs. Looked at in this way every medical board paper was a kind of forecast.

Almost at once the deficiencies in knowledge began to be apparent. It was found by experience that the organic view was not equal to the strain imposed on it. Those who had been content to recognize a sign and give a name to it perceived that this was not nearly enough. It was not enough even to find a particular germ in a laboratory, nor to discover by the use of X rays some abnormal condition. The laboratory, with all its