184 



muscles, which participation also is dependent upon the integrity 

 of the nerves which supply these seats. 



33. Hence we perceive that the stomach is liable (agreeably 

 with a general division) to the operation of three sets of proper- 

 ties; or is to be considered in respect of them, viz. the assimi- 

 lating, the spontaneous communicating (or the habitual), and the 

 occasional, or excited, comrnqnicating, properties. The first is 

 distinguished by its having no dependence, except upon arterial 

 blood; the second is inferred from the necessity which exists (for 

 the purpose of certain phenomena resulting from its function) of 

 a communication with another seat, and from the habitual or 

 regular occurrence of the phenomena dependent upon this com- 

 munication, when their seat is under no preternatural influence. 

 The inference of the third must always be dubious: for, although 

 the phenomena (as, for example, the digestion of food) are of an 

 occasional kind, and never take place but under the presence of 

 foreign substances, yet it does not follow, because the subject of 

 the operation of a power is sometimes present and sometimes 

 absent, that therefore the power itself is not always present. Yet 

 this seems the only criterion: and if it be allowed to furnish evi- 

 dence of any kind, it must be rated (in this example at least) at 

 that which is weakly presumptive. 



34. There are many other instances of affection and re-agency 

 which would illustrate our present topic, but they are well known, 

 at least the facts are well known: they are enumerated under the 

 head of sympathy, and belong less to physiology than to disease. 

 My business is not to detail particulars, but to seek after and 

 arrange those facts only which are important because they sub- 

 serve to the establishment of principles. It is here sufficient to 

 advert to the class of facts; merely observing, that affection 

 might commence in any part of a related circle; that the order 

 might proceed irregularly ; and that the complication is difficult to 

 be traced, because the natural order of affection, if any, may be 

 inverted, and if no natural one existed, the unnatural is not at 

 once recognized. But, granting the order of the affection of seats 

 to be made out, there is still the most difficult part of the process 

 to be analyzed, viz. the share in effects to be assigned respectively 

 to vital, chymical, and mechanical, means; the agencies of which 

 are rendered still more complex by their being liable to be con- 

 sidered, 1st, as results by addition and by privation; and, 2nd, 

 according to the two modes of operation between them, viz. the 

 direct and the mediate, of which we shall say more hereafter. 



35. There remains then, in viewing the stomach as an agent 

 with respect to other seats, to inquire with what other seats it may 

 be in this manner related: considering first the contiguous ones, 

 as the spleen, liver, pancreas, intestines, &c.; and then those 

 remote, if any. This examination, proposed rather in conformity 

 with a systematic design than with any expectation of useful re- 

 sults, belongs to the detail of physiology, and not to the indica- 

 tion of its topics. 



