6o 
Scientific Proceedings (42). 
with small droplets of fat. This amoeboid wandering of cells is 
a striking phenomenon in the cultivation of sarcoma in vitro but 
mitotic division of these cells is frequently seen in stained prepar- 
ations. "Ring" formation, as described by Harrison, is often 
observed especially when mouse sarcoma is cultivated in rat 
plasma. Within the ring where fibrin is absent the cells are seen 
growing along the cover glass. 
The growth of carcinoma in vitro differs quite markedly from 
that of sarcoma. At the end of eighteen or twenty-four hours 
there is noted around the piece of incubated tissue a narrow fringe 
of polygonal cells with large, distinct nuclei. This change is 
associated with a general flattening out of the specimen. During 
the next few days this fringe becomes a wide sheet of cells, spread 
out in a single layer, surrounding the original piece. The edge 
of this sheet of cells presents an irregular protoplasmic border with 
moving processes, — a picture almost identical with that described 
by Harrison for the growth of the epithelium of frog embryos 
cultivated in frog's lymph. In some preparations groups of cells 
invade the plasma at certain points, forming what might be termed 
"alveoli," with the fibrin network as a stroma. In addition to 
the growth just described, there may be, particularly during the 
first twenty-four hours, a migration of irregularly shaped cells, 
similar in type to those seen in sarcoma. Further study will be 
necessary to determine whether these are carcinoma cells or stroma 
cells. In stained specimens of growing carcinoma, we have ob- 
served mitotic figures at various periods up to the fifth day of 
incubation. We have not studied specimens of longer duration. 
This study seems to demonstrate how closely the character 
of the growth of tumor cells in the body may be simulated when 
these tissues are cultivated outside the body. 
