248 ELIOT R. CLARK AND ELEANOR LINTON CLARK 
DISCUSSION 
The subject of inflammation has been studied so extensively 
and the literature is so voluminous that it has seemed inadvisable 
to attempt an extensive review in this paper, and we shall merely 
indicate briefly some of the divergent views. Many of the early 
studies of Cohnhein, Metchnikoff, and Arnold were made on 
living material, and the general features of inflammation and 
many of the specific details, as discovered by them, are accepted 
by most pathologists. With regard, however, to the derivation 
and possible transformation of the cells taking part in inflam- 
mation, the widest difference of opinion may be found—among 
both pathologists and anatomists. The question as to the 
specificity of this group of cells, in normal growth, has not yet 
been settled by anatomists. On the side of non-specificity are 
found Maximow, Danchakoff, Weidenreich, and particularly 
Mollier (’11), who, although their studies have been confined 
mainly to early stages of embryonic development, believe, to a 
greater or less extent, in the interchangeability of endothelial 
cells, leucocytes, mesenchyme, and reticulum. Schulte (14) has 
gathered together data and opinions which apparently support 
this view and presented them in the form of a plausible though 
not entirely convincing argument. The specificity of the cells of - 
the group has been advocated particularly by Minot, Marchand, 
MacCallum, and Mall and his coworkérs—Sabin, Evans, E. R. 
Clark—although Mall apparently recognizes an exception in 
the ‘reticulo-endothelial’ cells of the spleen, liver and endo- 
cardium, and Evans (714) in the formation of free phagocytic 
cells from the Kiipffer cells of the liver, following injections of 
tubercle bacilli. 
In studies made on inflammation, the various views as to the 
possible transformation of one type of cell into another have 
been supported by the following: a) connective-tissue cells may 
be derived from leucocytes: Ribbert (’90), Metchnikoff (’93), 
Maximow (’02-03); b) endothelial cells from leucocytes: Ribbert 
(90); c) connective-tissue cells from endothelium: Ribbert (’90), 
Maximow (’05), in intense inflammation; d) endothelial cells 
