INTEESTITIAL INFLAMMATION. 



Ill 



one another. But now we know that a great majority of these 

 cells are colourless corpuscles which have emigrated from the 

 vessels. This is shown by an experiment of Cohnliehri s. The 

 mesentery of a living frog is stretched over a ring of cork, and 

 subjected to direct inspection. We can see how the veins dilate ; 

 how the colourless corpuscles first adhere to their inner surface, 

 and then put forth processes which penetrate their walls ; how 

 that portion of a process which has already escaped swells up, 

 and forms a kind of bridge, along which the whole substance of 

 the cell gradually creeps. Once through, the cells travel farther 

 by the aid of their amoeboid contractility ; if a special point of 

 the tissue is being irritated, that point becomes, in a general 

 way, their goal. There they continue to accumulate ; the result 

 of their accumulation being a certain quantity of that verv 

 embryonic tissue which serves as the starting-point of all further 

 changes (fig. 36). 



Fig. 36. 



^ ; "\~;:^,\:x:g;if,ii^]j)..;iii|[^ A^/^^ (%[('^\r'\jp^^^ 



CoJinJieivi's experiment. a. Yein; hh. Adjoining connective 

 tissue permeated by colourless corpuscles which have 

 migrated from the vessel; c. Column of red corpuscles. 



An older observation, which was first duly appreciated by 

 Billroth^ harmonises admirably with the above view of the deve- 

 lopment of plastic exudation or infiltration. It has been found 



