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Sanitary Effects from Drainage.

129

improvement which has taken place in the health of 24 towns by the drainage operations.

TABLE SHOWING IMPROVEMENT OF THE PUBLIC HEALTH BY

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Carlisle,
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field, 1845-52 1857-64 298 237 2633 217
Newport, 1845-49 1860-65 318 216 275 1873
Dover,

1845-57 1860-65 194 185 182 172 8 1847-54 1859-66 332 226 294 1913 Croydon, 1845-50 1857-61237 190 207 178 1845-53 1858-64 284 261 244 225

Leicester, 1845-51 1862-64 264 252 2364 225}| 14|
Merthyr, 1845-55 1862-65 332 262 292 2214 213
Chelten
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Cardiff,

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1843-53 1857-65|225209 203 187 14 9 93 7
Warwick, 1845-55 1859-64 227 210 2092 1913
Banbury, 1845-53 1857-64 284 205 214 1841 16
Penzance, 1843-50 1856-65 221 222 1974 2003
Salisbury, 1844-52 1857-64 275 219 253 1981

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In many of these towns the diminution of the mortality from cholera during its successive invasions is unquestionably due to improved drainage and water supplies. The diminution of thoracic complaints seems due to the drying of the soils, which, as a general rule, followed the construction of main sewers. At Salisbury fatal cases of pulmonary phthisis have been reduced to the extent of 49 per cent.; at Rugby, 43 per cent.; and at Worthing, 36 per cent. In those towns in which no decrease in the cases of phthisis has been observed, the disease, with but few exceptions, had not been excessive before the drainage operations, probably, in most cases, because the subsoil was naturally dry. Measles,

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130

Unhealthiness of Low-lying Places.

scarlatina, and whooping cough do not seem to be much affected by drainage works.

Heavy impertransible clay soils are unfavourable to persons disposed to rheumatic and tubercular complaints; whilst gravels and sands being loose and porous, though not productive of the above complaints, are dangerous when cholera and typhoid are epidemics. The granite and other primary rock districts are stated to be healthier, as are also the sandstone, limestone, dolomite, and chalk districts; whilst the dwellers on the drifts or alluvial soils are believed to be more liable to disease. Ponds, small lakes, slow moving rivers, situated in valleys, are most likely injurious to the occupants of houses close to their banks.

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Low-lying places are more liable to be ravaged by certain contagious diseases, such as, for example, Asiatic cholera. Dr. Farr directed attention strongly to this point in his report on the epidemic of cholera in London, 1849. The diagram shows the number of deaths per 10,000 of the inhabitants which occurred at the different heights above the level of the Thames. Those

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who lived at the level of the river were peculiarly exposed to the contagion of this frightful malady, the deaths amongst them having amounted to 174 per 10,000 living. On the other hand, at a height of 350 feet above the river level the deaths were only 6 per 10,000. Farr, however, pointed out the important fact that the greatest elevation was no protection against cholera.

In a

Mapother has shown (Lectures on Health, p. 487) that threefourths of the deaths that occurred in Dublin during the epidemic of cholera in 1866 took place on or close to the sites of ancient watercourses, now, for the most part, converted into sewers or filled up with mud. It is probable that the reason why cholera spreads most through low-lying districts is, that in such situations drainage being difficult, is often imperfectly carried out. low-lying place, well sewered, cholera would probably be less likely to spread than it would at a greater elevation with imperfect sewerage. It is not merely the death rate from zymotic diseases that is diminished by the proper drainage of the soil; for, as already shown, thoracic complaints are lessened by it, and in some clearly ascertained instances to a remarkable extent.

Pettenkofer remarks that organic matter decays much more rapidly in loose soils than in stiff clays. The Belgian chemist, Louis Creteur, had to disinfect the pits which contained the bodies of those slain at and near Sedan. He found that in the rubble, chalk, and other light soils, the bodies had mouldered away, but they were in a wonderful state of preservation in the heavy adhesive clays. The more porous the soil is the more rapidly organic matter decays therein, and the more readily the circulation of air and water proceeds. Such a soil is, therefore, the most abundantly inhabited by the lower forms of life. Pettenkofer shows that in these loose soils, and, indeed, in the earth generally, there is a large quantity of air usually richer in carbonic acid than the air above the ground, and that the underground-air is affected by the currents, temperature, &c., of the above ground-air. A strong wind playing upon the surface of the ground, outside a house, will sometimes force the gases contained in the ground into the interior of the adjacent houses. In this way, according to Pettenkofer, underground-air may be the means of introducing the contagia of certain zymotics into our dwellings.

Although disease is not confined to any season, there are certain periods of the year during which many maladies somewhat regularly attain their maximum intensity. Scarlatina is most prevalent during the December quarter. According to Dr. J. W. Moore, it produces in Dublin its maximum mortality in the 46th and its minimum in the 24th week of the year. Typhus is most prevalent in January and February, least so in June and July. Typhoid fever prevails more in summer than in winter. Whooping cough is most common in the winter and spring; and it is remarkable that a sudden rise of temperature increases at first this disease, but subsequently diminishes it. Diarrhoea and dysentery attack people more

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Mortality at Different Seasons.

frequently in autumn, least frequently in spring; whilst in the latter season rheumatic affections are most general. The mortality from small-pox is greatest during winter and spring. Out of 182 outbreaks of cerebro-spinal menengitis in Europe, enumerated by Simon, 24 occurred in October and November, 46 in December and January, 48 in February and March, 30 in April and May, 24 in June and July, and 10 in August and September. Asiatic cholera is essentially a summer disease, though an occasional outbreak of it in winter has taken place. The mortality from cholera makes its highest point in these countries in August or September.

Out of 29,308 deaths from diarrhoea recorded during sixteen years in London, two-fifths occurred during the thirtieth to the thirty-seventh week of the year inclusive. The greatest mortality was in the thirty-second or thirty-third, the least in the fourteenth week. The percentage of deaths from diarrhoea was 42 in summer, 40 in autumn, 10 in winter, 8 in spring.

In winter thoracic complaints-bronchitis, pneumonia, phthisis, &c. -are most prevalent, and are the chief factors in producing mortality. Dr. E. Smith has analysed the vital statistics of London for the period 1850 to 1854 (non-epidemic years), inclusive, and has ascertained the amount of mortality occasioned by each of the most important diseases in each quarter of those years. From his inquiries he has constructed the following interesting table :TABLE SHOWING THE EXCESS OR DEFECT IN THE PREVALENCE OF CERTAIN DISEASES AT EACH SEASON OF THE YEAR FROM THE AMOUNT WHICH WOULD HAVE OCCURRED HAD THE MORTALITY BEEN EQUALLY DISTRIBUTED THROUGH THE YEAR.

Disease.

Vital Changes.

1st Quarter. 2nd Quarter. 3rd Quarter. 4th Quarter.

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Explanation of Terms.

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CHAPTER XIV.

CONTAGION.

Most of the diseases which affect mankind arise spontaneously in each individual, and are not communicable from one person to another; but some maladies are propagated from the sick to the healthy. Any one completely isolated-that is, separated from contact or communication of any kind with all other personsmay still contract bronchitis, inflammation of the lungs, or paralysis; but a man so circumstanced would not be liable to small-pox, Asiatic cholera, or scarlatina. Diseases that arise spontaneously are termed sporadic-a term derived from the Greek word, sporadikos, separate or distinct; those which are acquired by contact with the person of, or emanations from, the sick are called contagious-from the Latin word, contagio, touch, or contact. Contagious diseases are in general epidemics '—that is, they simultaneously attack a large number of persons: but it is probable that a few non-contagious maladies are occasionally epidemic; in this class influenza is placed by some writers. The terms "contagious" and "infectious" are now generally used indifferently, and are equivalent to the expressive word catching. The term endemic2 is restricted to certain diseases, the range of which is confined to particular localities. Goitre, for example, is endemic in the Swiss valleys, malaria in the Roman plains, and ague in the marshy districts of India. All the diseases which appear in the epidemic form, or which are supposed to be contagious, are now generally placed in a group, and termed zymotic.3 Diseases of the same general nature, which affect the lower animals, are called epizootics.1

The more

In the present condition of medical science it seems rational to assume that the direct cause of every kind of zymotic disease is a distinct organised body, or entity, and not mere abnormal conditions of the ordinary ingredients of the air or soil. important zymotic diseases are small-pox (their type), typhus fever, typhoid fever, scarlatina, diphtheria, measles, whoopingcough, Asiatic cholera, and perhaps diarrhoea. It is a singular fact, that persons who have once suffered from a zymotic disease

1 Greek epi, on, and demos, the people.

2 Greek, en, among, and demos, the people.

3 Greek, Zyme, fervent. 4 Greek, epi, on, and zoon, an animal.

In a masterly essay (Typhoid Fever, its Nature, Mode of Spreading, and Prevention, by William Budd, M.D., F.R.S., London: Longmans, Green & Co., 1873), Dr. Budd has to my mind conclusively proved that enteric fever is a self propagating disease, and that it does not originate sporadically.

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