246 
MR. SAVORY ON THE DEVELOPMENT OF 
tlie cytoblasts free. However, when the fetal tissue is treated with water, there is a 
period just before the fibres break up when they become much more transparent, 
and the nuclei may be seen in their interior clustered together irregularly, and in 
absolute contact ; this fact, that the nuclei are in actual contact, is a most important 
one, for it proves very conclusively that they do not occupy the interior of cells. I 
have often earnestly sought for, but never yet detected, the appearance so generally 
figured in books of a muscular fibre as a string of nucleated ceils ; on the contrary, 
the nuclei, when they approach each other, are free cytoblasts, and they may be clearly 
seen to be in absolute contact. 
The nucleated cells which are seen in the blastema are no more concerned in the 
formation of muscular fibre than are the blood-cells. With regard to their purpose, 
it is to be observed that they are chiefly found in the layer of tissue investing the 
embryo, and if this exterior layer be carefully scraped off from the back of the embryo, 
and a portion of tissue be examined below the surface, nucleated cells, as compared 
with free cytoblasts, will be extremely rare. 
These nuclei, thus aggregated and invested, next assume a much more regular 
position. They fall into a single row with remarkable regularity, and the surround- 
ing substance at the same time grows clear and more transparent, and is arranged 
in the form of two bands bordering the fibre and bounding the extremities of the 
nuclei, so that they become distinctly visible, and the fibre at this stage presents 
the appearance represented in Plate X. fig. 3. The nuclei have now become de- 
cidedly oval and very closely packed together, side by side, so closely indeed that 
they appear as if compressed. Thus they form a single row in the centre of the fibre 
with their long axes lying transversely, and their extremities bounded on either side 
by a thin, clear pellucid border of apparently homogeneous substance. No structure 
can be discerned between the nuclei; they lie in close contact, except towards their 
extremities, and even appear as if pressed together. It is here to be remarked that 
this position of the nuclei is a strong additional argument against the supposition 
that they are or were contained in cells. If so, what explanation can be offered to 
account for the present arrangement? It occasionally happens, especially towards 
the extremities of a fibre, that some irregularity in the position of the nuclei may be 
discerned. They have not fallen into their places, but still remain as an irregular 
cluster, dilating the fibre by a separation of the lateral bands to a corresponding ex- 
tent, Plate X. fig. 4. More frequently, in the course of a fibre an occasional nucleus 
is seen, which instead of lying transversely is placed obliquely. 
The bands of tissue forming the borders of the fibre and bounding the extremities 
of the nuclei, at first thin and pellucid, soon increase in thickness by the addition of 
surrounding blastema to their external surface. They increase in breadth, and this 
increase is due to the addition of fresh material upon their exterior, and not to a de- 
posit upon their inner surface, for the extremities of the nuclei are not encroached 
upon, and the outline of the fibre, which is at first even and M^ell-defined, soon becomes 
