ENDOTHELIUM IN TISSUE CULTURES 45 
going on within the cells (W. H. Lewis, 719). Recent work has 
tended to confirm this view. Mrs. Lewis (’20 b, ’20 c) has shown 
that the addition of bacillus typhosus to the cultures causes a 
very rapid formation of similar vacuoles, and still more recently 
she has found that with the absence of dextrose from culture 
media vacuolization of the cells is more rapid and extensive than 
when dextrose is added. Miss Prigosen (’20, ’21), working in 
our laboratory, found that the cells in film preparations of the 
subcutaneous tissue of chick embryos showed a rapid accumu- 
lation of granules and vacuoles that had a great affinity for 
neutral red. 
Centriole and centrosphere. The centriole was not observed 
in the living cells, but in the fixed material could often be rec- 
ognized near the nucleus as a small granule about which the 
mitochondria and neutral red granules tended to accumulate, 
the former often assuming a more or less radial arrangement. 
In older cultures there frequently develops about the centriole 
a centrosphere which gradually enlarges (figs. 14, 15, 16; 19; 
20,21). This area varies in character ;1t may be quite homogene- 
ous, as in figures 16, 19, 20, or granular, as in figures, 14, 15. 
The enlargement of the centrosphere has not been followed in 
detail in these cells, but the process seems to be similar to that 
previously described for the mesenchyme cells (W. H. Lewis, 
95220). 
Nucleus. The nuclei are oval in form, long and narrow in the 
elongated cells, and short and plump in the spread-out flattened 
cells. The contour is usually smooth, but not infrequently in 
the older cultures it is uneven, being more or less irregular and 
indented. This appears to be the first indication of the process 
of budding and amitosis which results in the splitting of the 
nucleus into several, sometimes four or more, smaller nuclei 
(fig. 23). This process seems to take place only in the older 
cultures where other degenerative changes are evident. When 
a culture shows such changes there are usually many cells thus 
affected exhibiting various stages of the process. I have not 
actually followed this amitotic division in the living cells, but the 
evidence from the fixed material is very conclusive. In addition 
