266 



seat; or, in the latter, that some power, as one of affinity, must be 

 exerted by a distant seat, for the purpose of withdrawing proper- 

 ties from that which becomes the seat of disease: in either case, 

 implying a first change to have taken place in a related part, and 

 thus precluding in fact an origin of disease in any part; for the 

 same modes of causation must every where obtain. This view 

 suggests another origin of disease, or of the origin of the change 

 from the healthy to the predisponent state, viz. change happening 

 spontaneously in any given seat, and change happening in one seat 

 from a previous change in a related one: our difficulty belongs to 

 tiie first of these. 



18. The spontaneous change originating in a given seat hap- 

 pens from the operation of some cause which did not before pre- 

 vail. We have assumed that the externals are the same as before: 

 the cause in question, then, not being obtained from without, must 

 belong to the seat in which its effect is contemplated. If this cause 

 before resided in a structure in which it did not display itself by 

 effects, we can express its conditions only by saying that it was 

 latent or passive, and afterwards comes to be inferred from its 

 effect, or is active. We are not yet arrived at the origin of 

 these processes. 



19. By saying that a cause is latent, we intend that it is in a 

 state of combination in which it is not cognizable to our faculties; 

 if a cause is in this state which we call latent, or is better ex- 

 pressed as passive, why, it must be inquired, is this passive con- 

 dition changed? We here perceive the necessity of a causation 

 previous to that by which an effect is produced by a latent cause. 



20. This remoter causation admitted, we are still as far from 

 arriving at an origin of these processes; for every change must be 

 preceded by another, and the series, as well in the limited subject 

 which now occupies our regards, as in the universal scheme, must 

 be infinite. We see a certain state of constitution is preserved for 

 many years; at some period this state is altered, predisposition, 

 changes into disease, disease into death. In our physiology we 

 have remarked an order analogous in its kind, and some examples 

 still more striking may here again be mentioned. We perceive, in 

 the growth of the foetus, how, from a mere speck, bones, muscles, 

 arteries, veins, nerves, &c. are produced. We see the being thus 

 made, afterwards preserving a form, without any striking change, 

 except the gradual increase of the structures: after the lapse of 

 years, the attainment of puberty, glands secrete which never 

 secreted before, and the general changes which happen at this 

 period mark an important era in the history and existence of 

 the person. 



21. These are instances of that complication which has been 

 remarked to arise out of only two modes of causation. Causes are 

 infinite: their modes of producing effects have been said to be 

 only two by addition, &c. ; they may be still further simplified: 

 essentially, the mode of the operation of a cause is, that it exists; 



