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in this seat. From this view it is obvious that the sensible succession 

 is inadequate to determine the causation; for the brain may be the 

 the first to assume a change, by which it cures the disease in the 

 lungs; or the disease may cease in the lungs, from causation pro- 

 ceeding in this seat, and be assumed by the brain, or any other seat 

 which is predisposed to this result, under the relations which obtain 

 upon the cessation of a disease in a seat which it had hitherto 

 occupied. 



9. The alternatives here suggested must obtain in every case 

 in which the primary ceases upon the occurrence of the secondary 

 disease, but they do not necessarily obtain in all cases of related 

 disease: thus we say dentition disorders the bowels; this is a 

 case of simple succession, which, by analogies before explained, we 

 infer to be also one of causation. If, upon the occurrence of disorder 

 of the bowels, the process of dentition were suspended, we should 

 then have to determine whether the change preparatory to the 

 metastasis took place in the bowels or in the maxillary nerves. The 

 progress of consumption might be suspended upon the occurrence 

 of pregnancy: here consumption, as a related state, preceded 

 pregnancy, yet we know, as the cause in this instance is palpable, 

 that the seat of that change which produced the metastasis was the 

 uterus, or secondary related seat. Thus also the catamenia may be 

 checked by an exposure to cold which will produce rheumatism; 

 the change preparatory to, or causative of the metastasis is here also 

 in the secondary seat. From these and many similar examples, we 

 may perhaps conclude very generally, that the primary disease in 

 metastasis does not produce the secondary, but that the metastasis 

 itself is determined by a change which takes place in the secondary 

 seat. Yet this conclusion must not be universal, for we know that 

 the change which is preparatory to the metastasis may take place in 

 ihe primary as well as in tUe secondary seat, as when inflammation 

 of the brain succeeds the cure of erysipelatous inflammation of the 

 arm or face, by means of cold lotions: this also I have seen in"Ta 

 fatal example. We must rest then with the alternatives which will 

 respectively be adopted in the several instances, according to sensi- 

 ble evidence where this can be had, and according to the nearest 

 analogies from defect of better proofs. Without, then, comparing 

 instances which cannot be done accurately, so as to deduce a general 

 rule of probability, with respect to the origin of the processes of 

 metastasis, we will simply state the facts by a designation which will 

 agree with either of the above alternatives of the mode of causation. 



10. Related disease, according to our reduced division, is of 

 two kinds: 1st, as when a primary disease ceases upon the occur- 

 rence of a secondary; and, 2nd, as when a secondary merely suc- 

 ceeds to a primary disease. The former instances have been ex- 

 pressed by the word metastasis, which implies that the disease leaves 

 one seat and goes to another: this, however, is a conjecture without 

 proof, for an inflammation of the eye may be cured by a spon- 

 taneous diarrhoea; if the identical properties of the primary disease 



