MUSCLE. 131 
embryos ; but the deficiency in my researches may be sup- 
plied from the description given by Valentin (Entwicklungs- 
Geschichte, p. 268), from which the followmg passage is 
extracted: “ Long before separate muscular fibres can be dis- 
cerned, the globules of the primitive mass are seen, arranged 
in parallel lines, particularly when they are lightly pressed be- 
tween two pieces of glass. The granules then appear to he 
drawn somewhat nearer together, to become completely 
coalesced, in some situations, while at others the blending 
takes place only on the one or the other side, and to be com- 
bined into one transparent mass. In this way filaments are 
formed, which, in some situations, have an appearance like 
strings of pearls, at others, on the contrary, are less sharply 
indented ; they often also continue slightly puckered on one 
side, whilst the margin of the other has already become more 
straight. At a subsequent period, all trace of granules or 
division in the filament vanishes, and its outline becomes sym- 
metrically transparent and cylindrical. The muscular fibre 
usually undergoes no other change until the sixth month, ex- 
cept that its substance becomes somewhat darker and _ its 
cohesion closer. The first traces of transverse striz are ex- 
hibited in the sixth month. These fibres are the primitive 
fasciculi of muscle and not the primitive fibrils, which latter 
are formed by a splitting of the fasciculus into smaller fibres. 
From the period at which the muscular filaments become 
transparent and uniform, masses of globules, of a more or less 
spherical form and somewhat larger than the blood-corpuscles, 
begin to accumulate between them. They diminish again 
afterwards, and, blending with the gelatiniform mass which 
connects them, become converted into the connecting areolar 
tissue.” 
The youngest embryos in which I have investigated the 
generation of muscle were those of the pig, measuring three 
and a half inches in length. If a portion of one of the super- 
ficial dorsal muscles be removed from an embryo pig of that 
size, and examined under the microscope upon a black ground, 
a transparent gelatiniform mass is observed, in which parallel 
fibres (primitive fasciculi of muscle) run in close contact, 
having a whiter appearance than the surrounding gelatinous 
substance. As development proceeds, the transparent sub- 
