344 FLEXNER. 
a more considerable and important constituent is furnished by 
the nerve cells. First appearing as indifferent cells, entirely 
without orderly arrangement, they quickly undergo changes 
through which they become disposed in a regular manner, 
agreeing in position with the original cells which make up the 
parts, and after suffering some further alterations in form and 
staining capacity, may even be seen to develop fibers, which it 
is fair to assume are nervous in character. There occurs, also, 
at first an over-production of new cells, a surplus which in the 
end has disappeared. It would appear as if the new cells 
somewhat distant from the nerve trunks do not develop fibers, 
nor do they assume so orderly an arrangement ; and, moreover, 
they are the individuals which are finally lost. 
If this view of the regeneration of the nervous ganglia is 
correct, it must be admitted that a metaplasia of cells destined 
to become a simple external protective organ into the most 
highly differentiated structures of the body is, in these forms, 
possible. Barfurth! has pointed out the similarity in the 
regeneration of the epithelium of the skin and that of the cen- 
tral nervous organs of amphibian larvae, and attributes this to 
their common origin from the ectoderm. This conception, 
moreover, contains less that is startling in view of the obser- 
vations of Wolff and Erik Miiller? on the regeneration of the 
crystalline lens in tritons from the epithelium of the iris. 
JouHNs HopkKINS UNIVERSITY, BALTIMORE. 
1 Regeneration, Merkel-Bonnet’s Ergebnisse, i, 1891, 132. 
2 Archiv f. mikroskop. Anatomie ad. Entwickelungsgeschichte, xvii, 1896, 23. 
