Diagnosis. 95 



or in a rapid disappearance of the various lesions. The former 

 type includes such conditions as wounds, lacerations of external 

 or internal parts or the effects of poisons which rapidly and com- 

 pletely destroy the function of vital organs ; the latter, character- 

 ized by rapid recovery, is met in disturbances which are not fol- 

 lowed by structural changes, as convulsions, ansemic and hyperae- 

 mic states of the brain, of the skin and of mucous membranes. 

 On the other hand, diseases may continue for weeks or months, or 

 even years. They may begin suddenly or gradually and insidiously ; 

 may manifest alternately intensity and diminution in the severity 

 of their symptoms, fluctuations in the morbid processes (remis- 

 sions and exacerbations) ; may invade suddenly {paroxysmal; 

 paroxysm, invasion) and present interruptions {intermittent) in 

 the course, sometimes ending with gradual improvement {lysis, 

 resolution) , sometimes in a rapid, abrupt change {crisis, decisive 

 stage), leading to recovery or death. [By the course of the dis- 

 ease is meant the order of manifestation of the various stages or 

 events of the disease. It may be definite, regular or acute on the 

 one hand, when its events proceed in orderly manner and come to 

 a definite termination, or it may be indefinite, irregular or chronic, 

 when there is no fixed order of events and there is no set limita- 

 tion. Among the different types of the regular course two major 

 forms are recognized: (a) the continued course, where there is 

 but little variation in the intensity of the symptoms from time to 

 time, and (b) periodic courses, in which at certain definite times 

 special events manifest themselves. Among the periodic courses 

 are met, intermittent forms, in which there alternate periods of 

 absence of symptoms, known as intermissions, with periods of 

 presence of the symptoms in their intensity or paroxysms ; remit- 

 tent forms, in which there alternate periods of intensity of symp- 

 toms, known as exacerbations, with periods of diminution in in- 

 tensity, known as remissions ; and recurrent forms in which there 

 alternate comparatively long periods of absence of symptoms, the 

 intermissions, with similarly prolonged periods of their presence, 

 recurrences. The last form differs from the first in the length of 

 the alternating periods.] 



Diseases of brief duration are called acute diseases; those of 

 prolonged course, chronic. The former may last for a variable 

 period, up to fourteen days, while the latter extend over a course 

 of more than forty days : any instances falling between these 

 durations mav be classed as sub-acute affections. In case of 



