110 



INFLAMMATION. 



cells are largely the polynuclear leucocytes, but mononuclear forms and 

 eosinophiles may also pass out of the vessels. 



The cells pass between the endothelia through the cement substance, 

 which apparently is in some way changed in the inflammatory process. 







FIG. 30. EMIGRATION OF LEUCOCYTES FROM THE BLOOD-VESSELS OF THE MESENTERY OF THE FROG. 



Some of the leucocytes are clinging to the interior of the vessels ; some are passing through the walls ; some 

 are wandering away through the tissue spaces. There has been diapedesis of a few red blood cells. 



They may pass through very rapidly, but usually their progress is slow 

 aud often interrupted, so that cells may be seen motionless for a long 



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FIG. 37. EXUDATIVE INFLAMMATION IN THE WALL OF THE APPENDIX VERMIFORMIS. 

 Showing extravasated leucocytes in the vicinity of the blood-vessels with oedema of the surrounding con- 

 nective tissue. 



time in various stages of progress through the walls. A half minute, or 

 even less, may suffice for their passage, or they may be hours about it. 

 Thus, after a variable time, if the conditions have been favorable, the 



