254 
MR. SAVORY ON THE DEVELOPMENT OF 
from perfectly fresh embryos and from others which have been kept for some hours. 
The changes which occur in the appearance of the fibres during the earlier periods of 
development, after the embryo is removed from the parent, are very remarkable, and 
these changes are hastened by the presence of water. The blastema in which the 
fibres are imbedded, and from which they are formed, is clear, transparent, and 
apparently structureless, but the material which is recently added to the exterior of 
the fibre is rather opake and obscure ; and the obscurity is increased by the rough- 
ness of the surface which refracts the light irregularly, and very often gives a glisten- 
ing aspect to the fibre. As this blastema is developed into the substance of the fibre 
it clears up, it grows much more transparent, and its general characters and arrange- 
ment can be readily investigated. Now the blastema, when recently added to the 
exterior of the fibre, and which has not yet assumed the structure of the fibre, adheres 
but slightly and is readily detached, so that the fibres, which, when fresh, are quite 
obscure, by simple preservation for a short time, and more especially if placed in water, 
part with their more recent investment of blastema, and perhaps nuclei, and become 
clear and transparent. Hence, during the first stage of development, by simple pre- 
servation, and still more rapidly and effectually by the action of water, the fibre is 
altogether broken up. The delicate material investing and binding the nuclei toge- 
ther is easily dissolved, the nuclei separate, and no appearance of the early fibre 
remains. It is very common, however, in such a case, to see three, four or more 
nuclei attached together and in close contact, floating freely about, the recently added 
blastema having been detached from their surface. 
At a later period of their development, the action of water not only assists in 
removing the recently added and undeveloped layer of blastema which obscures the 
structure of the fibre, but it penetrates the interior, and renders its entire substance 
much more clear and pellucid, and the nuclei within more transparent. 
The Nuclei, which are such important agents in the development and maintenance 
of muscular fibre, and indeed of tissues generally, claim much more consideration 
than a passing notice*. These nuclei, when free as cytoblasts, may be observed in 
various stages of development. The younger ones are round or slightly oval, possess- 
ing a dark and distinct outline: their substance has a nebulous or faintly granular 
aspect. They very generally contain one or two well-marked nucleoli, which appear 
either as dark or as bright highly refracting spots, according to the focus at which 
they are viewed. The average diameter of these cytoblasts is from to 4o^oth 
of an inch ; the smallest are less than eWo^h. 
Tliey increase in size as age advances, and at the same time they become more 
* If the preceding description of the development of muscular fibre be a true one, it is another striking 
example of the truth and accuracy of the opinions which Mr. Paget has expressed with regard to the relations 
and functions of nuclei, and their extreme importance. — Lectures at the Royal College of Surgeons, May 1847. 
Lecture V. Surgical Pathology. 
