MODIFICATIONS OF THE SAME DISEASE. 1053 



prevail in spring, remittents in the early part of 

 summer; and after the powers of life have been 

 exhausted by long exposure to impure air of a 

 high temperature, they become merged in the 

 continued form of fever : 



5. That the most malignant varieties of con- 

 tinued fever are still more prevalent in tropical 

 and warm climates, where the predisposing causes 

 are more intense and constant in their operation : 

 but 



6. That in all climates and seasons very fatal 

 forms of continued fever are generated by con- 

 stant exposure to the concentrated malaria of 

 crowded dwellings, poor houses, hospitals, prisons, 

 and other ill ventilated dwellings ; or from con- 

 cussion of the brain, compound fractures, lacera- 

 tions, and other violent injuries, all of which 

 tend to diminish respiration, impair the vital 

 properties of the blood, and bring on a chill : 



7. And lastly, that the causes of intermittents 

 operate with less intensity, or for shorter periods 

 of time, than when they produce the continued 

 form of the disease, is demonstrated by the fact, 

 that, in the former, the paroxysm runs its course 

 in five, ten, w&& fifteen hours, on an average, after 

 which there is a complete intermission of all the 

 symptoms. 



But I have already shewn, that all the predis- 

 posing and exciting causes of disease tend to 

 produce a vitiated condition of the blood. Nor 



