Acute articular rheumatism is never absent; it occurs at all seasons of the year, although subject to moderate variations depending mainly upon atmospheric conditions. It is the general opinion that it prevails most during the cold and variable months of spring, but this is not true of every place, nor invariably of the same place. Indeed, Besnier,[1] after a long and special observation of the disease in Paris, concludes that there it is most frequent in summer and in spring. In Montreal, during ten years, the largest number of cases of acute rheumatism admitted to the General Hospital obtained in the spring months (March to June {20} inclusive), when they averaged 51 a month; 33 was the average for all the other months, except October and November, when 26-1/2 was the average. The statistics of Copenhagen, Berlin, and Zurich show a minimum prevalence in summer or in summer and autumn. [Footnote 1: _Dictionnaire Encyclopédique des Sciences Méd._, Troisième Serie, t. iv.] Occupations involving muscular fatigue or exposure to sudden and extreme changes of temperature, especially during active bodily exertion, predispose to acute articular rheumatism; hence its frequency amongst cooks, maid-servants, washerwomen, smiths, coachmen, bakers, soldiers, sailors, and laborers generally. While no age is exempt from acute articular rheumatism, it is, par excellence, an affection of early adult life, the largest number of cases occurring between fifteen and twenty-five years of age, and the next probably between twenty-five and thirty-five. A marked decline in its frequency takes place after the age of thirty-five, and a still greater after forty-five. It is not uncommon in children between five and ten, and especially between ten and fifteen, but is very rare under five, although now and then one meets with an example of the disease in children three or four years of age. While the acute articular affections observed in sucklings are, as a general rule, either syphilitic or pyæmic, some authentic instances of rheumatic polyarthritis are recorded. Kauchfuss's two cases among 15,000 infants at the breast, Widerhofer's case, only twenty-three days old, Stager's, four weeks old, and others, are cited by Senator.[2] [Footnote 2: _Ziemssen's Cyclop. of Pract. Med._, xvi. 17.] An analysis of 4908 cases of acute rheumatism admitted to St. Bartholomew's Hospital, London,[3] during fifteen years, and of 456 treated in the Montreal General Hospital during ten years,[4] gives the following percentages at given periods of life: London. Montreal. Under 10 years, 1.79 % | Under 15 years, 4.38 % From 10 to 15 " , 8.1 % | From 15 to 25 " , 48.68 % " 15 to 25 " , 41.8 % | " 25 to 35 " , 25.87 % " 25 to 35 " , 24.5 % | " 35 to 45 " , 13.6 % " 35 to 45 " , 14.2 % | Above 45 " , 7.4 % Above 45 " , 9.5 % |