568 OF NUTRITION. 



nutrition, is always more liable than another to be the seat of local manifesta- 

 tion of blood disease; it is, in common language, the "weak part/' 1 And it 

 frequently needs the concurrent operation of a local depressing cause, to fix and 

 develop the action of the constitutional cause, or blood disorder ; thus, a rheu- 

 matic or gouty diathesis may exist for some time (as when, to use a common 

 expression, the disease is " flying about" the patient), and yet the poison may 

 not have sufficient potency to produce an attack of acute inflammation, until 

 the vitality of some particular organ becomes depressed by cold, over-exertion, 

 or some similar influence, which would not have itself engendered the diseased 

 action, had it not been for the concurrence of the morbid condition of the 

 blood. Thus we seem justified in concluding, that, whether the causes of In- 

 flammation act directly upon the tissues of a part, or whether they act upon it 

 through the intermediation of the blood, their effect is to produce a depression 

 in its vital powers, which manifests itself in a deficient formative activity, and 

 in an increased tendency to degeneration ; and that this is one of the primary 

 and essential conditions of Inflammation. 



610. This view is by no means inconsistent with other manifestations of In- 

 flammation which have been supposed to indicate " increased action ;" and, in 

 fact, it is in such striking accordance with the phenomena presented by the 

 movement of the blood, when these are interpreted by the principles already 

 laid down, as to afford a powerful confirmation to both doctrines. The usual 

 condition of the vessels of an inflamed part is one of dilatation ; and this may 

 be fairly attributed to the lowered vitality of their walls, whereby they yield 

 too readily to the distending force of the current of blood. But this current 

 moves too slowly ; and its retardation may gradually increase, in the part most 

 intensely inflamed, to the point of complete stagnation. Now this altered rate 

 of movement cannot be attributed to any general cause : nor can it be accounted 

 for by the change in the diameter of the vessels ; for, on the one hand, it may 

 occur with a constricted state of the vessels, whilst, on the other, in the vessels 

 surrounding the inflamed part, which partake of the dilated condition, the flow 

 of blood is so far from being retarded, that it usually takes place more rapidly 

 than usual. But it may be fairly considered as the result of the lowered or 

 suspended nutritive activity of the part, which will tend to retard or entirely 

 check the motion of blood in the systemic capillaries, just as the want of aera- 

 tion retards or checks the pulmonary circulation ( 527). It is quite true that 

 a larger amount of blood passes through a limb, of which some part is in a state 

 of active inflammation, than passes through the corresponding sound limb; 

 but this is far from indicating " increased action" in the inflamed part, being 

 dependent upon the augmented flow of blood through the tissues which sur- 

 round it ; and if the whole of a limb be in a state of inflammation passing on 

 to gangrene (as occurs when a " frost-bitten" limb has been incautiously warmed) 

 the amount of blood which passes through it is diminished. It would be just 

 as erroneous to assume the elevated temperature of an inflamed part as a sign 

 of " increased action" in it; for this elevation is no doubt attributable in part 



1 A patient under Dr. W. Budd's care had Smallpox soon after a fall on the nates ; the 

 pustules were thinly scattered everywhere, except in the seat of former injury, and on this 

 they were crowded as thickly as possible. So a man who was under Mr. Paget's care 

 with chronic inflammation of the synovial membrane of the knee-joint, and general 

 swelling about it, having been attacked with Measles, the eruption over the diseased knee 

 was a diffused bright scarlet rash. So Impetigo appears about blows and scratches in 

 unhealthy children, and Erysipelas first attacks the seat of local injury in men with 

 unhealthy blood. Perhaps as good an example as any is afforded by the uniform limita- 

 tion of the inflammation consequent upon the introduction of Vaccine matter into the 

 blood, to the spots in which the puncture was made; notwithstanding that the whole mass 

 of blood is affected by it, as is shown by its incapacity for subsequently developing the 

 poison of smallpox. 



