24 BOVINE PATHOLOGY. 



while red corpuscles, aggregated into bundles,, lie nearer 

 the centre of the vessels. Migration now occurs as a 

 result especially of the amoeboid activity of the white 

 corpuscles, whereby they are able to penetrate the proto- 

 plasmic, and, therefore, living walls of the capillaries. 

 Thus they, and sometimes a few red corpuscles, pass into 

 the tissue interspaces, and intermingle with the new 

 generation of cells produced by the proliferation of the 

 tissue elements. At the same time the serous portions of 

 the stagnated blood transude through the walls of the 

 vessels, and thus originates effusion as well as exudation, 

 for they are rich in solids. Effusion of serum and exuda- 

 tion of lymph are early accompaniments of inflammation ; 

 they occur, to a more or less degree, in almost every case, 

 and are the principal cause of swelling. This depends, 

 also, to a certain extent, upon the conditions of the 

 vessels in the parts bordering on that inflamed. They 

 are very full of blood coursing rapidly through them, are 

 in a state of hypersemia or congestion. The presence of 

 this large quantity of rapidly flowing blood, with, perhaps, 

 also the rapid tissue changes in the inflamed part, 

 generates the characteristic heat; to the congestion and 

 amount of blood, even in the seat of disease, the eedness, 

 characteristic of inflammation, must be attributed ; while 

 pressure from effused material and distended vessels is 

 the cause of the painful nature of the process. The pain 

 present must also be attributed to heightened sensibility 

 of the nervous structures. It is related to the hardness 

 of the part, hence inflammation of unyielding organs is 

 most painful. The reproductive activity of the tissue 

 elements replaces their normal function, and the rapidity 

 of new cell formation prevents the elaboration of inter- 

 cellular substance, hence the intercellular material accu- 

 mulates in a state of imperfect development as fluid, and 

 tends to increase the added liquid and plastic material 

 which has been thrown out. Effused liquid material can 

 be taken up again by the capillaries and lymphatics of a 

 part with facility if the vessels have not themselves 

 undergone change. When the latter complication is 



