almost driven from the surface. It accumulates within, and congestions and inflammations are produced. Free action on the inner surface of the body for a time relieves the congestions, and enables the circulation to proceed."-Martin on The Influence of Tropical Climates.

217

CHAPTER XIII.

DISEASES OF THE RAINY SEASON.

ness.

WITHIN this range we meet with the most unhealthy period of Unhealthithe tropical year, the commencement of the rains and its termination; and sometimes from meteoric causes, during the whole of the rains, fevers of the most severe type are prevalent. The temperature at the commencement of the rains falls a great deal; the occasional showers produce a refreshing and delightful feeling; the atmosphere becomes very moist and warm; vegetable and animal life, which before were in a state of dormant vitality, now put on renewed life and vigour ; decomposition of animal and vegetable matter, accelerated by the heat and moisture, is very rapid. The atmosphere is very heavy in the mornings and evenings, and the horizon is covered with fog and haze. When the heat of the sun is felt, it produces a great increase in the perspiration, which through the moist air seems to exude from the various pores of the body by transudation, and not by evaporation. The muscular system becomes very much relaxed, the action of the heart weak; there is a congestive state of the internal organs through the venalised condition of the blood, and its receding from the surface.

When the rains have not been plentiful at the commencement, only coming occasionally, and being succeeded by very hot days, when there has not been much thunder and lightning before and during its commencement, fever of the most relaxing and congestive character, or epidemics of yellow fever,

Circumstan

ces producing

unhealthi

ness.

Medico

statistical

report.

are generally the consequence. Dysentery and diarrhoea are also prevalent in places where good water cannot be obtained. In Western Africa the commencement of the rains is more unhealthy than their termination, although this period is generally very sickly.

There are many circumstances which combine to render the season unhealthy

1. The occasional occurrence of rain, with the subsequent heat, leads to the formation of stagnant pools, rich in vegetable and animal putrescent matter.

2. The clearing of the fields by farmers in preparation for sowing, deprives the country of the salutary effects of vegetable life, in absorbing the poisons of malarious effluvia emanating from stagnant pools and other sources.

3. The diminished vitality of all the functions of the body; and,

4. The great want of electric agencies in the atmosphere (thunder and lightning), and the consequent diminution of nature's universal disinfectant-ozone.

To prove that the commencement of this season is even more unhealthy to the native population, I shall here quote at length my medico-statistical report of Anamaboe station, from 1st April to 20th May 1861, forwarded to the civil authorities :

The numerical relations between sickness and health during the half section of the second quarter of the year, form an interesting data for inquiring into the relative healthiness or unhealthiness of the different sections of the year.

From meteoric circumstances, as well as practical observations, it is now universally acknowledged that the second quarter of the tropical year is the most unhealthy part of the year.

During the first quarter of the year the number of daily patients attending the dispensary to the 31st of March, amounted to 920; whilst during the half section of the second quarter, viz., from 1st April to 20th May (scarcely two months), the number of daily patients was 1114.

The average daily number of patients who attended the dispensary for the first quarter was 12.2, whilst for the sectional part of the second quarter it was 22-2, showing an increase of 10 per cent of daily attendance. From these facts alone it is evident, that at this quarter of the year the station under consideration was far more unhealthy than the preceding. I shall now enter into detail respecting the different diseases treated, and shall follow the division I had formerly adopted, viz. :

I. ZYMOTIC.

II. CONSTITUTIONAL.

III. LOCAL.

IV. VIOLENCE AND ACCIDENTS.

There were no less than 566 cases of zymotic diseases daily treated. The most frequent were-rheumatism, 116; and gonorrhoea, 100. It is remarkable that the number of dysenteric cases was fewer than was expected for the time of the year; this may be accounted for from the fact, that the natives possess potent medicines for it, and, except in extreme cases, they do not apply to the dispensary; so also with fever.

There were 83 cases of constitutional diseases; and 386 of local diseases, of which ulcers (100) were the most frequent; violence and accidents numbered 79 cases.

I shall now conclude by stating, seriatim, the number of daily cases treated in the dispensary, as well as those daily treated in the houses of Poll Tax patients.

I. ZYмOTIC.-Ophthalmia, 60; diarrhoea, 12; dysenteria, chronica and acuta, 30; febris intermittens, 22; hemicrania, 6; rheumatisma, 116; gonorrhoea, 100; strictura urethræ, 40; scabies, 42; dysmenorrhagia, 60; porrigo, 18; orcheitis, 60. II. CONSTITUTIONAL.-Debility, 45; phthisis pulmonalis, 10; scrofula, 28.

III. LOCAL.-Hemiplegia, with spasmodic contraction, 60; otitis, 26; bronchitis, 54; pneumonia, 18; dyspepsia, 6; constipatio, 85; odontalgia, 10; psoriasis, 8; ulcers, 100; pediculæ, 8; hydrocele, 9.

Ozone-its effects on malarious fever.

IV. VIOLENCE AND ACCIDENTS.-Vulnus incisum, 30; contusio, 24; fractura, 12; snake bites, 13.

The unhealthy season commences later in the Gambia region than on any other part of the coast, as the commencement of the rains is later. The sickly weather begins about the end of June and during July. At Sierra Leone and Liberia the rains commence early in May, and the sickness then begins to manifest itself; and it is a known fact, that the report of epidemic is generally heard of one or two months at Sierra Leone ere it is heard of in the Gambia. On the Gold Coast station the commencement of the rains is not so unhealthy, from the exposed state of the different stations to the constant sea breeze and the perfect ventilation which is the result. Lagos and other parts in the Bights, not being so much exposed as the Gold Coast, are very unhealthy.

One of the causes of the unhealthiness of the beginning of the rains is the diminution of atmospheric ozone. The effect of this important agent in malarious fever has occupied my particular attention. Being stationed for some time in the hotbeds of malaria, I had ample opportunities of observing the various changes which take place in the system when under the operation of both.

The quantity of ozone in the atmosphere has an indisputable effect on the influence of fever in malarious districts; when it exists in large quantities cases of fever are generally few, and when in small quantities, fever is more frequent and of longer duration.

When the quantity of ozone in the atmosphere is very large, one may with impunity expose himself, in places where malaria is rife, without the manifestation of its constitutional effect for days or even weeks; and although a large quantity of ozone in the air destroys evidently a large quantity of the substance we know as the harbinger of fever, itself, at the same time, undergoing decomposition and destruction, yet still that which remains may be inhaled in sufficient quantity to lead to a paroxysm, although prevented from manifesting