INVOLUNTARY MUSCULAR FIBRE. 551 
rious other tissues; and from the apparent identity in nature of these corpuscles 
in the different textures in which they are found, and especially in voluntary, as 
compared with involuntary muscle, it is scarcely conceivable that in the latter 
case exclusively they should be the nuclei of oblong cells constituting the proper 
muscular tissue.” 
Mr Etmis, then, agrees with Mazonn in believing that the tapering fibre-cells 
of KoLiiker owe their shape to tearing of the tissue; and he regards the nuclei as 
mere accidental accompaniments of the proper muscular structure, probably be- 
longing to the sheath of the fibres, which, according to him, are of rounded form 
and uniform width. 
The distinguished position of Mr EL.ts as an anatomist makes it very desirable 
that his opinion on this important subject should be either confirmed or refuted, 
and the object of the present paper is to communicate some facts which have re- 
cently come under my observation, and which, I hope, may prove to others as 
unequivocally as they have done to myself, the truth of KoLiiKEr’s view of this 
question. 
In September last, being engaged in an inquiry into the process of inflamma- 
tion in the web of the frog’s foot, I was desirous of ascertaining more precisely 
the structure of the minute vessels, with a view to settling a disputed point re- 
garding their contractility. 
Having divided the integument along the dorsal aspect of two contiguous toes, 
I found that the included flap could be readily raised, so as to separate the layers 
of skin of which the web consists, the principal vessels remaining attached to the 
plantar layer. Having raised with a needle as many of the vascular branches as 
possible, I found, on applying the microscope, that they included arteries of ex- 
treme minuteness, some of them, indeed, of smaller calibre than average capilla- 
ries. A high magnifying power showed that these smallest arteries consisted of 
an external layer of longitudinally arranged cellular fibres in variable quantity, an 
internal exceedingly delicate membrane, and an intermediate circular coat, which 
generally constituted the chief mass of the vessel, but which proved to consist of 
neither more nor less than a single layer of muscular fibre-cells, each wrapped in 
a spiral manner round the internal membrane, and of sufficient length to encircle 
it from about one-and-a-half to two-and-a-half times. Fig. 18. (Plate XV.) repre- 
sents one of these vessels as ‘seen under a rather low power, and shows the ge- 
neral spiral arrangement of the fibres of the middle coat. Fig. 19. is a camera 
lucida sketch of the same artery highly magnified, in which I have for the most 
part traced the outline of the fibres on the nearer side of the vessel only, but 
one fibre-cell is shown in its entire length wrapped round nearly two-and-a-half 
times in a loose spiral. In some other vessels the muscular elements were 
arranged in closer spirals, as in figs. 20 and 21. They are seen to have 
more or less pointed extremities, and are provided with an oval nucleus at 
