166 CHAPTER 18. 



blood is slower, though regular. 3rdly. The flow of blood becomes irre- 

 gular, and oscillates. 4thly. The current almost ceases, and the vessels 

 are distended with coloured corpuscles. 5thly. If the stagnation be not 

 relieved, the serum will be exuded through the walls of the vessels ; and 

 perhaps ultimately, by reason of ruptures occurring in the over-distended 

 coats of the vessels, the red particles of the blood may pass out. 



332. Arrest of the circulation at the inflamed part. 



In the inflamed part the circulation is to a certain degree arrested, 

 to a greater or less degree according to various circumstances. This 

 arrest is due 1st to an altered vital relation between the tissues and 

 the blood ; 2nd to increased viscidity or adhesiveness of the blood in the 

 part ; 3rd to diminished action of the vessels themselves, owing to ner- 

 vous prostration, on account of which they cease to assist in the function 

 of circulation ; 4th sometimes to a mechanical impediment, such as 

 agglomeration of the corpuscles, a foreign body, or a clot of fibrin ; 5th 

 to a tendency in the vessels themselves to become dilated or varicose at 

 parts and contracted at other parts. 



333. Original seat of the stagnation. 



The various tissues in health derive their nutriment from the blood 

 contained in the capillaries or minute vessels which permeate their 

 structure. Hence in disease the disturbance of the regular functions of 

 the tissue is first felt in those vessels. Hence, again, the blood con- 

 tained in them is soonest affected and altered in character. Hence the 

 stagnation or " stasis " of the circulation commences in them earlier than 

 in the larger vessels. 



334; Changes which occur in the blood after leaving the seat of inflammation. 



There is stagnation and sometimes complete arrest of the blood in the 

 inflamed part. In that part the blood, as stated above, is viscid and 

 altered in its character. It leaves the part but slowly. The change in 

 its character has been produced by the action of the diseased tissue on 

 it. As soon as it gets free from that morbid action, it rapidly regains 

 among the healthy tissues its fluidity and proper consistence. The vital 

 processes by which nature restores the blood in a great degree, but per- 

 haps not entirely, to a healthy condition are difficult to explain. An 

 illustration may serve better than an explanation. If a clear stream 

 runs through a muddy pond, it will issue out from it somewhat disturbed 

 and thick ; but after again running a short distance over a gravelly 

 bottom, and exposed also to the wholesome influence of oxydisation from 

 the air, it will soon be as clear as ever. Again it must be remembered 

 that, unless the seat of the inflammation is very extensive, the amount 

 of blood which has become altered in its character from the action of 

 the diseased tissue is very small when again mingled in the mass of the 

 general circulation. 



