in Ethiopia full of the bodies of dead locusts. The poison generated in both cases is the same; the difference is merely in the degree of its potency. Nature with her burning sun, her stilled and pent-up wind, her stagnant and teeming marsh, manufactures plague on a large and fearful scale. Poverty in her hut, covered with her rags, surrounded by her filth, striving with all her might to keep out the pure air and to increase the heat, imitates Nature but too successfully; the process and the product are the same, the only difference is in the magnitude of the result. Penury and ignorance can thus, at any time and in any place, create a mortal plague." 1

Dr Southwood Smith has been accused of ignoring the fact that those suffering from fever can communicate the disease to others-of "infection," as it is called. But he did not. He shows, on the contrary, that the atmosphere of a room such as that spoken of in the passage just quoted must have the power of inducing fever in others besides the patient. He even says that "the poison formed by the exhalations given off from the living bodies of those affected by fever is by

1 Treatise on Fever, p. 324.

far the most potent febrile poison derived from animal origin."

Then, it might be asked, of what consequence is it to insist on the disease being non-contagious If fever-patients can give fever to others, it is a mere matter of words whether you choose to call it "contagious" or "infectious."

It is, however, of the utmost consequence to fix the attention on the difference; because, if that is done, the real seat of the danger will be clearly seen, and those whose duty it is to enter the rooms of the sick will know that their danger rarely lies in touching the patient, and may be prevented by abundance of fresh air and scrupulous cleanliness.

In order to emphasise this side of the truth my grandfather wrote as follows (and, though it may seem to require qualification, the general truth of his remark will be admitted by all): “No fever produced by contamination of the air can be communicated to others in a pure air- there never was an instance of such communication."

The form of poison given off from a fever patient is, besides, not so much to be feared as other forms of that poison, because, though

it is potent, it has not a wide range; when let out into the fresh air, it is so far diluted that its power is reduced to a minimum.

An epidemic, he asserts, can only arise from some cause sufficient to affect a whole district. Continually we are brought back to observe this universal cause of fevers; to see that, whether in the sudden falling off of an army to half its numbers, or in the prostration of a whole ship's crew on approaching shore, or in the plague devastating Cairo, this one source may be traced as the true one. Bad air comes from the marsh near which the army is stationed; bad air, poisoned by decaying vegetation, comes off shore to the ship; bad air enters the houses of Cairo. We are shown that Cairo is the birthplace of the plague, because it is a city crowded with a poor population; because it is built with close and narrow streets; because it is situated in the midst of a sandy plain at the foot of a mountain, which keeps off the wind, and is therefore exposed to stifling heat; and, above all, because it has a great canal which, though filled with water at the inundation of the Nile, becomes dry as the river gets lower, and thus emits an

intolerable smell from the mud and from the offensive matter that is thrown into it.

Besides being thus shown that, in all places in which epidemics appear, some sanitary defect may be found, we are shown that they come back and back to the same places, and that, if these defects are removed, the epidemics will not return. So we are led on to the great idea that they are preventible.

The facts advanced to prove these principles have not, of course, the wide range, the distinct statistical exactness, of those which the further progress of sanitary science has now enabled people to bring forward; but it is very interesting to see how all further advance has been but a development of the principles brought forward in this Treatise on Fever,' just as it was itself but a development of those brought forward five years before. Hardly any investigations had yet been made, but the results which research would bring to light are here foreshadowed. Even the direction which such research would take is indicated, for we are told, at the end of the chapter which treats of the "Causes of Fever," that—

"Further inquiries are necessary - such as, whether the vegetable and animal poisons we have been considering be the only true, exciting cause of fever;1 by what means its general diffusion is effected; on what conditions its propagation depends; by what measures its extension may be checked and its power diminished or destroyed; what circumstances in the modes of life, in the habits of society, in the structure of houses, in the condition of the public streets and common sewers, in the state of the soil over large districts of the country as influenced by the mode of agriculture, drainage, and so on, favour or check the origin and propagation of this great curse of civilised, no less than of uncivilised, man."

Not a mere article or book contained the result of such inquiries. They occupied the greater part of his life, and that of many others. Their outcome is the present state of sanitary knowledge.

If some people think there was nothing new in the view of epidemics insisted on in this

1 Modern investigations have proved, for instance, that contaminated water or milk will produce an epidemic as well as contaminated air. But all these poisons arise from bad sanitary conditions.-G. L.