305 



10. If a primary ceases upon the occurrence of a secondary 

 disease, it ceases, either because the primary disease, has left its 

 seat, and produces the secondary, or because the secondary, being 

 established by causes either wholly or in part independent of those 

 engaged in the primary disease, is so related with, as to cure the 

 primary disease. The first of these happens from progressive 

 change, in the seat either of the primary or secondary disease; the 

 second, either from communication of properties from the secon- 

 dary independent state of disease to the primary one, or from 

 privation of the properties of the primary, in agreement with a 

 new relation opened between it and the properties engaged ia 

 the new state of secondary disease. The causation also in these 

 cases must be dubious: such again are the alternatives. If this 

 subject were not already sufficiently complex, it may be suggested 

 that, in an analysis of these processes of disease, we have also to 

 define the share in them which might belong respectively to the 

 properties of life, to the mechanical state of the structures, and the 

 chymical conditions of the fluids. These latter are to be con- 

 sidered as re-agents. 



11. In attempting to discriminate the mode of causation ia 

 related diseases, we can only scrutinize the succession, which will 

 rarely afford much light, because the processes of disease in related 

 seats, although in the beginning there might be an obvious antece- 

 dent, will in their course appear synchronous, or so mixed that a 

 precise order cannot be distinguished. Such, however, are the 

 indications for minute inquiry; and, to obviate a reliance upon the 

 false theories which would explain these phenomena, it has been 

 proposed merely to state the facts, that, of related diseases some 

 are substituted, or curative, and others are a mere extension of 

 disease to related seats. It appears from the facts, that disease in 

 some, or many seats, may be cured by an agency which is extended 

 from a related seat; and this agrees with the design of employing 

 remedies which operate not upon the seat of the disease, but upon 

 some other. This agreement, and the foundation of the design, 

 we shall presently have occasion to examine. 



s 



