Fixation Reaction to Specific Precipitation. 137 
become phagocytic and take up small particles of agar and coagu- 
lated blood serum. Similar observations we made recently in 
the case of growing tubular cells of the kidney and of carcinomatous 
cells 1 and probably also in the case of ingrowing stroma cells. 
D. While the parenchymatous cells penetrate onto the coagu- 
lum in a more or less definite arrangement which to some extent 
corresponds to the normal arrangement of the parenchyma cell, 
the form of cell columns or of tubules being retained respectively, 
the connective tissue cells on the other hand grow as single cells 
often sending out long drawn out stellate processes in the coagu- 
lum, the various connective tissue cells being loosely connected 
by such processes. This arrangement enables the stroma cells 
to penetrate into the coagulum with relatively greater ease than 
is possible in the case of parenchyma cells. 
E. Stroma as well as parenchyma cells (including carcinoma 
cells) show a definite direction in which they grow into the coagu- 
lum, both having the tendency to proceed along the fibers which 
form in the coagulum and to follow, if at all, for a short distance 
only a course vertical to the direction of the fibers in the coagulum. 
The connective tissue cells seem however in consequence of their 
isolated and independent mode of growth and of moving occasion- 
ally to be able to penetrate into the coagulum in other directions 
more easily than parenchyma cells, but they also usually follow 
the road of least resistance. 
F. We recognize therefore variations in the relative importance 
of stroma and parenchyma in the case of the growth of different 
organs. In a provisional way we may assume that the parenchyma 
of those organs or tissues that normally show an additive (expansive) 
growth (active outgrowth) like carcinoma and stratified epithelium 
of the skin show likewise an infiltrative growth in coagula (in 
gelatinous culture media generally) and that those organs that 
normally or during regeneration do not show additive (active 
expansive out) growth, but rather compensatory hypertrophy, 
do correspondingly not show a strong tendency to infiltrative 
growth, when growing in culture media (testicle, ovaries). In 
the latter class however the stroma may or may not show infiltrative 
1 The same observation has been recently made in the case of tumor cells by 
R. A. Lambert and F. M. Hanes, Journal Exp. Med., Vol. XIII, 191 1, p. 495. 
