INFLAMMATION, 251 



It does occur to a very considerable extent in the capillaries, 

 and from them emigration of the red corpuscles also takes 

 place. The leukocytes, as their number increases, do not re- 

 main in the neighborhood of the vessels from which they 

 migrated ; while the red globules, which have no power of 

 amoeboid movement, remain near the vessel from which they 

 escaped. The migration of the leukocytes continues to such 

 an extent that, as there is no room for them in the interstices 

 of the tissue, some reach the free surface of the mesentery. 

 By the end of six or seven hours the phenomenon is no longer 

 to be seen. 



The serous membrane becomes opaque, due to an exudate of 

 serum from the bloodvessels, which, by coagulating and en- 

 tangling in its meshes of fibrin white and red blood-cells, 

 forms on the surface of the mesentery a sort of a pseudo- 

 membrane. 



These blood- vascular changes have been observed in warm- 

 blooded animals ; in the wing of a bat and the mesentery of 

 a rabbit. 



The dilatation of the bloodvessels was supposed by Cohn- 

 heim to be due to the direct injury of the vascular walls by 

 the trauma, producing chemical and molecular changes of the 

 greatest importance. These changes in the vascular walls, he 

 suggested, caused an increased friction of the blood against 

 the walls, which was supposed to explain the retardation of 

 the current. A further consequence was the greatly increased 

 permeability of the vessel-walls, permitting cellular and serous 

 exudations. We cannot state with certainty the exact cause 

 of the dilatation of the vessels. That it is not due to vaso- 

 motor paralysis is shown by the fact that w 7 hen inflamma- 

 tion occurs in a part in which the vaso-motor nerves have 

 been cut the vessels still further dilate. 



The slowing of the current is an important factor in the sub- 

 sequent phenomena of margi nation and diapedesis. This 

 importance has been experimentally shown by the fact that 

 artificial acceleration of the current induced by the intra- 

 venous injection of a 6 per cent, salt solution materially re- 

 tards the development of these phenomena ; and directly so 

 in proportion to the degree of this acceleration. 



An increased permeability of the vessel walls has been ex- 



