84 INFLAMMATION.
Theories of Cell Migration-—Cobnheim explained the passage of
leucocytes by their spontaneous amceboid movements. The re-
tardation of the blood current, which is itself a consequence of
arterial dilatation, causes them to collect at the sides of the vessels,
where they lose their spherical form and become flattened aguinst
the wall, and at the samc time commence those movements, con-
sisting in the protrusion of protoplasmic processes, which they
exhibit elsewhere. hese processes, sent out in all directions,
extend themselves whore they mect with least resistance, through
certain gaps or stomata which Cohnheim believes to exist in the
veins between the epithelial cells of their inner membrane and
in the capillaries between the similar cells which he believes to
constitute their walls. The middle and outer coats of the veins
are also supposed by him to possess interstices sufficient to allow
the leucocytes to pass. The red corpuscles, which have no spon-
taneous movements, he supposes 1o be forced by mere increase of
hydrostatic pressure through the openings, already enlarged by
the passage of the leucocytes. On this view, then, the structure
of the vessels remains normal, though possessing a natural adap-
tation for cell migration ; whilo others, on the contrary, deny the
existonce of these openings in the yascular walls, and regard the
permeability of the vessels to their contents as a morbid pheno-
menon, and the essential cause of exudation and cell migration.
According to Dr. Burdon Sanilerson, the retardution of the blood current (which is the first stage of stasis), and the exuda- tion of liquor sanguinis, as well as that of the white and red corpuscles, are all due to the same cause, namely, a ‘local change in the vascular walls.” With respect to the nature of this change, he says that ‘‘fhe mode in which an injury changes the bving substance of the yascular walls so as to mako them permeable to the blood is unknown. The nature of the change itself’ is also unknown.” From certain appearances observed in the formation of new yessels he is, however, led to infor ‘that the primary change consists in the transition of the material from the formed into the plastic condition; from a state in which it is resistant, because inactiye, to one in which itis more living, and therefore nore labile,”
Theories of the Cause of Stasis—Whether this phenomenon be regarded as the cause, the consoqnonce, or the meve accompani- ment of exudation, its causation is a question of much interest, and was described in the first edition of this work as the great and unsolved problem of inflammation. Henle regarded it as due to the inspissation of the blood plasma, resulting from exudation ; this condition causing endosmotic changes in the red corpuscles, by which they are disposed to aggregate. Rokitansky suggested in addition the formation of fibrinous coagula. We do not doubt that the changes wrought by exudation, draining away of liq. sanguinis, multiplication of white corpuscles, and coagulation of the fibrine, may all exercise considerable influence in prolong- �
