ETIOLOGY.—Intestinal inflammation is more prevalent in the Northern, Middle, and Western than in the Southern States. There is no relation between the distribution of malarial and intestinal diseases: in some regions where malarial disease is rife there is very little disease of the intestines. Limited areas in Lower Mississippi, Eastern Kentucky, Eastern North Carolina, etc. have a special predisposition to diseases of this class.6
6 F. A. Walker, Statistical Atlas, 1874, table v. p. 3; also plates xlii. and xlv.
During the Civil War diarrhoea and dysentery were more frequent and fatal in the central region than in the Atlantic and Pacific regions.
It is difficult to compare the relative liabilibity of the native and foreign-born populations in the United States to intestinal disease. Inasmuch as children, among whom the bulk of such cases occur, bear such a small proportion to the adult foreign population, allowing for differences due to this cause, statistics show that the foreign-born race has a very distinct predisposition to these forms of disease.7 The Swedes, Norwegians, and Danes have a marked susceptibility to intestinal diseases; the English and Welsh have the same tendency; but the Irish have a comparative immunity. The colored race is more prone to intestinal than to malarial diseases in the Middle States, but there is the reverse susceptibility in the Northern and Southern States.
7 The number of children under ten to 1000 native population is 306; number of children under ten in 1000 foreign population, 47 (F. A. Walker, "Relations of Race and Nationality to Mortality in the United States," Statistical Atlas, 1874, p. 213).
Under ten years more males than females have enteritis, in the proportion represented by the figures 362 and 299. After ten the predisposition of the two sexes is about the same.
The summer is the season when diarrhoea is most prevalent and most fatal. June, July, and August are the months in which the greatest number of cases occur and in which there is the highest mortality. The extraordinary death-rate in these months in cities is of course due to the influence of summer heat on children, and the death-rate from diarrhoea and entero-colitis is chiefly among infants under one year. But among adults the same rule holds. The highest monthly mortality from acute diarrhoea among the U.S. troops (white) between 1861 and 1866 was 147, in July, 1862; the next highest was 114, in August, 1862. June and September were after these the most fatal months. According to the census of 1870, the most fatal month is August.
Elevation of temperature in the summer months is the cause of the prevalence of intestinal catarrh and of its great mortality among infants and children. The number of deaths bears a direct ratio to the degree of heat, the highest death-rate occurring in seasons of unusual high temperature.8 The effect of excessive or prolonged heat is to arrest or weaken the digestive processes; undigested masses in the stomach or the intestines act as foreign bodies and produce inflammation.
8 Among the numerous publications bearing on this subject, those contained in The Sanitary Care and Treatment of Children and their Diseases (Boston, 1881) are of especial value. S. C. Busey's article contains much valuable matter on the relation of summer heat to illness and mortality among children.
Sudden changes of temperature from cold to heat or from heat to cold develop diarrhoea. If the air is at the same time saturated with moisture, the effect of a change in temperature is greatly intensified. In the first hot days of June there is on the Atlantic coast, especially in cities, a rapid increase in the number of cases of gastro-intestinal disturbance. A larger number of children are taken ill in June than in August. The child in time becomes habituated to heat, and if not attacked early runs less risk of illness in the later months. A sudden or unusual exposure to low temperature, as in lying on damp ground, leads to the same result. The check to perspiration after violent exercise is especially provocative of diarrhoea. In these instances the congestion and consequent inflammation of the mucous membrane are brought about through the effect of heat or cold upon the peripheral nervous system. Cold may act more directly by the driving of suddenly-cooled blood from the surface of the body to the interior. External burns belong to the same category, as they lead to extensive inflammation, sometimes to ulceration, of the duodenal mucous membrane through reflex influence. A case is reported of a boy aged twelve years who after an external superficial burn of the left thigh was taken with profuse diarrhoea which ended fatally in three hours (Ziemssen).