236 Royal Society :— 
PROCEEDINGS OF LEARNED SOCIETIES. 
ROYAL SOCIETY. 
January 16, 1862.—Dr. William Allen Miller, Treasurer and Vice- 
President, in the Chair. 
*On the Development of Striped Muscular Fibre in Man, Mam- 
malia, and Birds.”’ By J. Lockhart Clarke, F.R.S. 
In the domestic fowl, until the beginning of the fifth day of incu- 
bation, the so-called voluntary muscular tissue consists only of a 
crowded multitude of free nuclei imbedded in a finely granular blas- 
tema; the nuclei are round, oval, pyriform, and somewhat angular, 
with granular contents. On the fifth and sixth days of incubation, 
fibres becomesuperadded under two forms,— Ist, as processes extending _ 
from the ends, or from the sides of nuclei; 2nd, as narrow bands, 
either uniformly delicate and pale, or bordered by darker outlines, 
and containing nuclei at variable intervals. They are most numerous 
near the surface of the layer, and probably belong, at least partly, 
to the muscular layer of the skin. In every case their first stage of 
development is conducted on one general plan, which consists in the 
fibrillation of the blastema along the sides of nuclei, to which the 
fibrillee so formed become adherent. Sometimes these fibrillee or 
lateral fibres enclose a single nucleus with conical processes of blas- 
tema, so that the object occasionally presents some resemblance to a 
fusiform nucleated cell. More frequently, however, they enclose a 
linear series of nuclei at variable distances from each other, but 
cemented together by blastema, which sometimes assumes around 
each a more or less definite shape. In the formation of the paler 
fibres, however, a series of neighbouring nuclei may sometimes be 
seen first to collect round themselves granular masses of a more or 
less fusiform appearance, and then to coalesce with each other, in an 
oblique or alternately imbricate way. Sometimes a series of the 
nuclei themselves overlie each other in an imbricate form like a 
number of coins, and are cemented together by a common layer of 
blastema. 
In the early part of the seventh day of incubation, numerous fibres 
of a much larger and more striking description suddenly make their 
appearance in the nucleated blastema. They originate, however, on 
the same general plan as the others, in a fibrillation of the blastema 
between, or along the sides of, a variable number of nuclei; but the 
process goes on to form aggregate masses of a much larger kind, and 
of a more or less oval, fusiform, or cylindrical shape, in which the 
nuclei are ultimately enclosed. Some of these bodies have a ve 
striking resemblance to organic muscular-fibre-cells, which, aieorte 
ing to my own opportunities of observation, are developed on the 
same general plan, that is, by the formation of sarcous substance, 
first, in the shape of fibres or lateral bands along the sides of a nucleus 
more or less encrusted with blastema, so that the organic muscular- 
fibre-cell would appear to represent an early stage in the development 
of the striped muscular fibre. 
