MUSCULAR MOTION. 
variety. Such is the case with thé ductus cho- 
ledochus in Birds, and probably in Mammals, 
and in the ureters and vasa deferentia. The 
bronchial tubes may be mentioned under this 
head as the best marked example of this ar-_ 
rangement. The trachealis muscle consists evi- 
dently and entirely of the unstriped fibres, and 
the same may be traced down the brorchial 
ramifications as far as the air-cells themselves, 
though not into them. The distinctive charac- 
ters of this form of muscle may here be une- 
quivocally discerned, and if anatomists had 
been better acquainted with them, there would 
not have been room for those disputes regarding 
the muscularity of the bronchial tubes which 
have so long attracted the interest of practical 
physicians. Recently, indeed, there has been 
added to the satisfactory evidence of anatomy 
the well proved fact that these fibres may be 
excited to contraction by the galvanic stimulus.* 
In the case of other glands it is still unknown 
how far the muscular coat invests the ramifica- 
tions of the duct; it is most likely that it gra- 
dually ceases a short way within the organ, 
and at least it seems clear that no portion 
of the secreting membrane itself is ever in- 
vested by it. 
e. Of the distribution of the striped and 
wnstriped fibres in the animal kingdom.— 
The striped fibres have been found in all ver- 
tebrated animals, and in Insects, Crustacea, 
Cirropods, and Arachnida. Future researches 
will probably discover them even more exten- 
sively diffused. But in the lower animals, 
especially when they are of small size, we find, 
as formerly mentioned, that the distinctive cha- 
racters of the two varieties begin to merge into 
one another and be lost. The transverse stripes 
grow irregular, not parallel, interrupted ; a fibre 
at one part will possess them, at another part 
wili be without them; and even the peculi- 
arities of the unstriped fibres are sometimes no 
longer to be met with in parts which are un- 
doubtedly muscular, as the alimentary canal 
of small insects. It is evident that here the 
elementary fibres, if of their usual bulk, would 
be greatly disproportioned to the requirements 
of the case, and consequently even the minute 
ultimate fibre seems to be reduced within 
limits which remove from it those anatomical 
characters by which alone we can positively 
aver its existence. Considering, however, the 
circumstances which have been already ad- 
verted to in this article, as determining the size 
of the elementary fiore in all animals, we 
Should not be justified in denying the same 
_ muscular tissue to exist here which in the higher 
and larger forms of life assumes the figure 
and bulk of the elementary fibre; and by the 
same mode of reasoning it may be concluded, 
that a tissue having the same properties as the 
Striped fibre, and indeed essentially identical 
with that of which they consist, may possibly 
be the effective agent to which are due those 
wonderfully vivacious movements witnessed in 
the bodies of many of the minutest infusoria, 
where the best microscope can hardly do more 
* Dr. Williams, on Discases of the Chest, last. 
edition, Appendix. 
519 
than discern the organs thus put in motion. 
And it seems far from an unphilosophical view 
of the nature of ciliary motion, to refer it to 
the contractions of a ‘tissue not entirely dif- 
ferent in kind from the muscular. The ele- 
mentary fibres of muscle, diminutive though 
they be, and hardly discernible with the eye, 
are yet gross organs in comparison with those 
which the microscope enables us to conceive 
capable of being formed out of them, without 
any necessary destruction or even injury of 
their contractile power. 
J. Chemical constitution —There is little to 
add on this subject to what will be found under 
the head of Fisrine. By the aid of the mi- 
croscope, however, our knowledge has been 
rendered somewhat more precise, as to the 
chemical properties of the elementary struc- 
tures existing in the fibres. If any substance 
capable of dissolving fibrine (as liq. ammoniz) 
be added to the muscular fibre, this is seen to 
swell, to lose more or less completely its trans- 
verse and longitudinal markings, and to exhibit 
at once those corpuscles or cytoblasts, which 
before lay concealed among the sarcous ele- 
ments. ‘These corpuscles and the sarcolemma 
are not affected, but the sarcous elements are 
almost entirely taken up. But for however 
long atime the fibre be exposed to the alka- 
line menstruum, there will always remain a 
kind of web, of extreme tenuity and trans- 
parency, from which the sarcous elements ap- 
pear to have been withdrawn. This may be 
seen in a transverse section of a muscle that 
has been thus treated, then washed and dried. 
I have not been able to detect in it any sort of 
structure.* 
( W. Bowman. ) 
MUSCULAR MOTION.— Under this 
head it is intended to consider the contractility 
of muscle, its source, the stimuli that excite 
it, and the nature of the minute movements 
occurring during the act of contraction. 
a. Of the contractility of muscle—This 
subject having already been ably discussed in 
this work (see Contractitity), I shall here 
confine myself to such a brief statement as 
may appear to be required by the advance of 
knowledge since the publication of the article 
in question. 
1. Is it a property inherent in the muscular 
bre? Are we to believe in the ‘ vis insila’ of 
Haller?—The supporters of this opinion have 
always been exposed to the objection that in 
the cases of contraction adduced by them as 
the effect of a topical or immediate stimulus, 
the isolation of the muscle from all connexion 
with nervous fibrils has not been demonstrated. 
Moreover, what has generally been regarded as 
their strongest ground, viz. the statement that 
involuntary muscles are not capable of being 
excited to contraction by irritation of their 
nerves, has lately been shown by the numerous 
(* The principal facts relating to the morbid 
states of Muscle will be found in the articles 
HEART, Morbid States of, and HYPERTROPHY and 
ATROPHY. An historical sketch of the subject 
concludes the article MUSCULAR MoTIon.—ED. ]} 
9 
