244 
MR. SAVORY ON THE DEVELOPMENT OF 
the appearance of a cylinder is produced, which becomes more perfect as the parti- 
tions between the cells disappear*. 
These observations have not been confirmed. M. Lebert has more recently 
studied the development of striated muscular fibre chiefly in the heart of the chick 
The following is a short abstract of his peculiar description of the process. “The 
rhythmical contractions of this organ become very manifest and regular towards the 
thirty-sixth hour of incubation ; nevertheless, it is at this time composed of nothing 
else than organo-plastic globules or elementary cells imbedded in a granular blas- 
tema. Between the fourth and fifth days of incubation are seen in the midst of the 
mass of globular particles certain elongated subcylindrical bodies, sometimes grouped 
together in a reticular manner ; these bodies being the first rudiments of the muscular 
fibres, not merely in the heart but also in the other striated muscles, are designated 
by M. Lebert ‘ myogenic cells.’ Between the seventh and eighth days the ‘ organo- 
plastic globules’ undergo a considerable diminution, and the 'muscular substance 
presents a more complete development. A longitudinal striation shows itself in the 
contents of the cylinders, which seems partly due to the grouping of the granular 
particles of which these contents consist ; the transverse striations do not show them- 
selves until some time afterwards The organo-plastic globules which at first 
separated the primitive cylinders gradually disappear ; the cylinders approach one 
another, and before the end of embryonic life they are found to be grouped into 
fasciculi:};.” 
When many months since I began to study the development of muscular fibre, it 
was with the hope of being able to add something to what appeared to be a very im- 
perfect explanation of the process. The results of these investigations I have endea- 
voured to communicate in this paper. It may be as well to state at once that the 
conclusions I have arrived at are, for the most part and in all important points, com- 
pletely at variance with the account which is generally believed to be the true one. 
I can therefore only meet the doubts with which 1 must expect the following state- 
ments to be received, with the assurance that they have not been hastily or carelessly 
advanced, and by an appeal to the verdict of future inquiry. 
These observations have been made for the most part upon foetal pigs, but they 
have been confirmed by repeated examinations of foetal calves, lambs, goats, rabbits, 
rats, and human embryos. 
In very small embryos, specimens of muscular tissue for microscopical examina- 
tion are most conveniently obtained from the dorsal region. If therefore a portion 
* Philosophical Transactions, 1840, 1841. -I* Annales des Sciences Nat. Juin 1849, Mars 1850. 
t Principles of Human Physiology, by Dr. Cakpenter, 1853, pp. 305, 306. I have recently read a paper 
by Dr. Holst, giving a short account of some observations by Reichert and himself on the development of 
muscular fibre. From some of the engravings which accompany the paper, he has probably seen, although I 
think misinterpreted, the condition of the fibre in what I have described as the second and third stages of deve- 
lopment. 
