SS KOLILIKER, ON MUSCULAR FIBRE. 
After other observations tending to disprove the existence 
of the minute canals supposed by Leydig to exist in muscular 
fibre, Kolliker says, “ with respect to the interstitial granu- 
lar tracts in the muscular fibre of the frog, that one thing 
in particular should be remarked,—that the opaque fat- 
granules, which are frequently noticed in frog’s muscle, origi- 
nate in a metamorphosis of the pale granules above described. 
These molecules, in chemical constitution, appear to differ 
but little from the contractile substance—they are merely 
of rather more difficult solution in caustic alkali, and more 
soluble in acetic acid. 
This interstitial granular substance would appear to exist 
in the muscular substance, perhaps, of all animals. It is 
particularly well developed in the muscles of insects, naked 
amphibia, the sturgeon, &c.; in the latter instance, however, 
the molecules in their normal condition were observed only 
in the pale-coloured muscles. In the reddish subcutaneous 
muscles they appeared to be replaced by series of fat-mole- 
cules, of far larger size, especially near the tendons, and 
giving the muscle a more peculiar character than is presented 
even in the muscles affected with the highest degree of fatty 
degeneration. 
In the mammalia and in man the interstitial granules are 
very delicate and pale; and they are distinctly recognisable 
only when in a state of fatty degeneration, in which state 
they exhibit, in a transverse section, an appearance like that 
seen in the muscles of the frog. 
As regards the physiological import of the interstitial 
granular substance, Kolliker throws out as a probable hypo- 
thesis, that the granular tracts in question originate directly 
in the disintegration of the fibrils, and represent the normal 
molecular change of the muscular substance. He admits, 
nevertheless, that this explanation is attended with many 
difficulties, and that other suppositions may be entertamed 
with apparently nearly equal justice. 
He sums up the results of his inquiries into the ultimate 
structure of muscle as follows : 
1. All muscular fibres contain a large number of well- 
marked, vesicular nuclei with nucleoli, which are either 
parietal and affixed to the sarcolemma (human), or uni- 
formly dispersed throughout the contractile substance (Am- 
phibia), or even, as in certain embryos, disposed in series in 
the centre of the primitive fasciculus (some muscular fibres 
of Amphibia.) 
2. Inthe case of the contractile substance of the muscular 
fibres, it appears to him, as regards the higher animals, most 
