hifiamation. Plogesis. Phlegmasia. 43 



Finally they separate, together with the cell protoplasm, forming 

 two daughter cells. 



This cell proliferation under the action of an irritant is com- 

 mon to the vegetable kingdom in which galls, and tumors are 

 formed in this way. It is a remarkable feature of these multi- 

 plying cells that they not only lose their power of developing the 

 tissue in which they formerly lay, and have all their vital powers 

 devoted to proliferation, but they acquire the amoeboid power of 

 their ancestors, the embryonic cells, which they further resemble 

 in size. Indeed these cells are freely spoken of as embryonal 

 cells, and the tissue formed by their massing together as embry- 

 onal tissue, and there is a widespread impression that they revert 

 entirely to the form and characters of the embryonic cell. In 

 some respects, however, they are unlike. The modified tissue 

 cell of inflammation presents a nucleus of horseshoe outline, or 

 after division of the nuclei they together retain this semi-circular 

 outline ; it has the power of actively digesting the adjacent tis- 

 sues as the embryonic cells do not, and again it does not possess 

 the power of differentiation into widely different tissues as does 

 the early embryonic cell. It may be called a reversion, in the 

 direction of the embryonic cell, however, since it reacquires a 

 number of its functions. 



Migration of ^vhite blood cells. This is another, and in vas- 

 cular tissues the main source of the great cell accumulation in the 

 inflamed tissue. This process was observed by Waller in 1846, 

 but was given its true importance through the later observations 

 of Cohnheim. The migration takes place through the walls of 

 the capillaries and veins only, and the migrating cells are largely 

 of the poly-nuclear variety of leucocytes. These remaining ad- 

 herent to the inner wall of the blood vessel may be seen to have 

 a small portion of their substance projected through the wall and 

 appearing as a small buttonlike projection on the outer side. 

 This gradually increases, while the remaining portion of the cell 

 on the inner side of the wall correspondingly decreases until the 

 whole cell is lodged in the tissue outside the vascular wall. The 

 time occupied in passing through is very varied. It may be 

 wholly accomplished in half a minute, and again hours may be 

 required for the complete passage of a single leucocyte. The ex- 

 planation of this migration has been sought in the supposed 



