THE

QUARTERLY REVIEW.

ART. I.-MALARIA AND THE MOSQUITO.

1. Lectures on the Malarial Fevers. By William Sydney Thayer, M.D. London: Henry Kimpton, 1899.

2. On the Role of Insects, Arachnids, and Myriapods as Carriers in the Spread of Bacterial and Parasitic Diseases of Man and Animals. A Critical and Historical Study. By George H. F. Nuttall, M.D., Ph.D. 'Johns Hopkins Hospital Reports.' Vol. VIII.

3. Instructions for the Prevention of Malarial Fever. Liverpool School of Tropical Medicine. Memoir I. Liverpool: University Press, 1899.

4. Report of the Malaria Expedition of the Liverpool School of Tropical Medicine and Medical Parasitology. By Ronald Ross, D.P.H., M.R.C.S., H. E. Annett, M.D., D.P.H., and E. E. Austen. Liverpool School of Tropical Medicine. Memoir II. Liverpool University Press, 1900.

5. A System of Medicine, by many Writers. Edited by Thomas Clifford Allbutt, M.A., M.D., LL.D. Vol. II, 1897; Vol. III, 1897. London: Macmillan and Co.

6. A Handbook of the Gnats and Mosquitoes. By Major Geo. M. Giles, I.M.S., M.B., F.R.C.S. London: John Bale, Sons, and Danielsson, Ltd., 1900.

7. Reports to the Malaria Committee, Royal Society, 1899 and 1900. By various Authors. London: Harrison and Sons, 1900.

IT has been

T has been said that one half the mortality of the human race is due to malaria. This may very well be an exaggeration, but there can be little doubt that of all the ills that flesh is heir to malaria is the most deadly, and exercises the most profound influence on the distribution and activities of Vol. 192.-No. 384.

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man. It will be seen later that the disease is most rife where the densest populations are found; and the mortality of such a closely crowded area as India gives some idea of the enormous loss of life and the wide-spread suffering caused by this disease. In 1892, out of a total population in India of 217,255,655, the deaths from all causes reached the figure of 6,980,785. Of these, 4,921,583 were ascribed to 'fever.' All these fevers were not of course malarial, but comparison with other statistics leads to the belief that a high percentage of them was caused by malaria. Major Ross states that in 1897 over five million deaths in the same country were recorded as due to 'fever,' and that out of a total strength of 178,197 men in the British army in India 75,821 were treated in the hospitals for malaria. Fifty years ago the loss from malaria amongst the European population of India was 13 per thousand. With improved methods of living and more skilful treatment this has been reduced to 7 per thousand; but the native, who is slow to change his ways, and usually averse to modern methods of treatment, still retains a very high fever death-rate, over 18 per thousand. During the years 1887-1897 the average mortality in Italy attributed to malaria was 15,000 a year, and 2,000,000 patients annually suffered from 'fever.'

Apart from the mortality due to this disease, the amount of suffering and the decline in human power and activity which it entails deserve careful attention. Compared with the number of patients, the number of deaths is by no means large. In round numbers, out of every thousand soldiers in the British army in India in 1897, 420 men were attacked by malaria, but only one in a thousand died; even in the 'most malarious' districts the death-rate only amounted to 6 per thousand. In Sierra Leone, a district much more fatal than any in India, the average death-rate of the white troops, based on hospital records extending from 1892 to 1898, is estimated by Major L. M. Wilson at 42.9 per thousand, whilst that of the coloured troops is 59 per thousand. On the other hand the European troops show an annual admission to the hospital of 2134 cases per thousand, and the non-European troops one of 1056 per thousand. These figures probably under-estimate the amount of fever amongst the troops. It must be remembered that many soldiers who have slight attacks of fever do not present themselves at the hospital, whilst of those who do a considerable number are only detained for slight treatment, and are never entered on the hospital books, and so are not recorded on the returns.

From the statistics quoted above, it appears that of our

soldiers in India three out of every seven suffer from an annual attack of malaria sufficiently pronounced to be recorded on the medical books, whilst our soldiers on the west coast of Africa have an average of at least two attacks a year, and a considerable number of them die. There is no reason to believe that the civil population of India or West Africa is in any degree more exempt from the disease than the military, but the statistics in the latter case are more readily accessible.

Malarial fever, when it does not kill, leaves great weakness behind; and all who have watched malaria patients, or patients. who are already recovering from an attack, cannot fail to have noticed the listlessness and want of interest in their surroundings and the lack of inclination to work that they all show. Apart from the mortality, the disease probably levies a heavier tribute on the capacity of the officers and officials who administer the British Empire than does any other single agency.

Before describing the organism which causes all this misery a word or two must be said about the distribution of the disease. Roughly speaking, malaria is confined to a broad irregular belt running round the world between the 4th isothermal line north of the equator and the 16th line south. It is, however, said to occur occasionally outside these limits, for instance, in Southern Greenland and at Irkutsk in Siberia; but until recently the accurate diagnosis of the disease has been difficult, and too much reliance must not be placed on these statements. The chief endemic foci of the disease are along the banks and deltas of large rivers, on low coasts, and around inland lakes and marshes. Malaria is common all round the Mediterranean region: it was well known to, and its symptoms were clearly noted by, the early physicians since the time of Hippocrates. They even recognised the difference between the mild spring and summer attacks and the more pernicious effects of the autumnal fever. In France there are several prominent malarial districts: the valley of the Loire and its tributary the Indre, and the valley of the Rhone; also the sea coast stretching from the mouth of the Loire to the Pyrenees, and again the Mediterranean seaboard. It occurs in Switzerland, and is found in Germany along the Baltic coasts, and on the banks of the Rhine, the Elbe, and other rivers, and in many other parts. Scarcely a province in Holland is quite free from it, and it is found in Belgium and around Lake Wener, in Sweden. It extends along the lower Danube and around the Black Sea, and spreads across Russia, being especially prevalent along the course of the Volga and around the Caspian. From Europe it spreads over Asia Minor, and affects all southern Asia as far as the

East Indies, but in Japan it is curiously rare. It is also infrequent in Australia-where it is confined to the northern half of the continent—and in many of the Pacific Islands; and it is unknown in the Sandwich Islands, New Zealand, Tasmania, and Samoa. In America it is more common, and of a more severe type on the Atlantic sea-board than on the Pacific; in the last hundred years its northern limit is said to have retreated in the centre of the continent, though some observers think it is creeping further north in the Eastern States. In a mild form it is known around the Great Lakes, and in Canada and in New England; but it reaches a high degree of intensity in the Southern States, Mexico, Cuba, and Central America, where it probably played a greater part in ruining the projected Panama Canal than all the corrupt financing of the speculators in Paris. It extends throughout the warmer parts of South America, and is known in a virulent form all over Africa except the extreme South.

In Great Britain it used to flourish. The following extract from Graham's 'Social Life of Scotland in the Eighteenth Century' shows what a part it played in the life of the Scottish peasant.

'The one ailment to which they were most liable, and in which dirt had no share, was ague. This was due to the undrained land, which retained wet like a sponge, and was full of swamps and bogs and morasses in which "green grew the rushes." Terribly prevalent and harassing this malady proved to the rural classes, for every year a vast proportion of the people were prostrated by it, so that it was often extremely difficult to get the necessary work of the fields performed in many districts. In localities like the Carse of Gowrie, which in those days abounded in morasses and deep pools, amongst whose rushes the lapwings had their haunt, the whole population was every year stricken more or less with the trouble, until the days came when drainage dried the soil, and ague and lapwings disappeared.'

In England it was once very prevalent. James I died of 'a tertian ague' at Theobalds, near London, and Cromwell succumbed at Whitehall to a 'bastard tertian ague' in 1658, a year in which malaria was very widely spread and very malignant; and it is only within recent memory that the fen districts in Cambridgeshire and Lincolnshire, Romney Marsh in Kent, and the marshy districts of Somerset have lost their evil reputation for ague. The older chemists in the towns in the fen districts still recall the lucrative trade their fathers carried on in opium and preparations of quinine with the fenmen during the first half of this century; but with the

improved drainage of the fens this has all disappeared, and at present cases of endemic malaria appear to be unknown in England, though sporadic cases turn up at rare intervals. It was also very prevalent along the estuary of the Thames, both on the Essex and Kentish marshes. Pip in 'Great Expectations says to his convict :

"I think you have got the ague." "I'm much of your opinion, boy," said he. "It's bad about here," I told him. "You've been lying out on the meshes, and they're dreadful aguish.'

Ireland, which appears at first sight peculiarly adapted for the disease, seems to have been remarkably free from it. It may be that the strong antiseptic quality of the peaty bog-water hinders the development of the larval mosquito.

Turning now to the cause of the disease, it is interesting to note that the discovery of the organism which produces all this misery and death took place just about the time when Koch was making his far-reaching investigations into the cause of tuberculosis. In 1880 Koch was at work on the tubercle bacillus ; and in the same year a French army surgeon, named Laveran, looking down a microscope in a remote military station in Algiers at a preparation of blood taken from a malarious soldier, recognised for the first time the small organism which has played a larger part in human affairs than the greatest politician or general that ever lived. This small organism is an animal, not a plant. It belongs to the great group of singlecelled organisms, mostly microscopic in size, called Protozoa, and it lives as a parasite inside the body of other animals, from which it abstracts what nutriment it needs. Before describing its structure and life-history a word or two must be said about its surroundings in the body of man.

That blood consists of a fluid in which enormous numbers of cells called blood-corpuscles float is now a matter of common knowledge. These corpuscles are of two kinds, the red and the white, but the red surpass the white in number, in proportions ranging from 300 up to 700 to 1. A cubic millimetre of blood contains about five million red corpuscles; and since these act as the carriers of oxygen from the lungs to the tissues all over the body, and on their return journey carry away the carbon dioxide from the tissues to the lungs, where it is given off, it is obvious that the presence of a parasite in the red corpuscle will have a most serious effect upon the welfare of the body.

a

Before Laveran's discovery, Lankester had described parasitic organism living in the blood-cells of a frog, and