Discovery that the Veins of the Bat's Wing (which are furnished with
valves) are endowed with Rythmical Contractibility, and that the on-
ward flow of blood is accelerated by such contraction. By T. Wharton
Jones.—In entering on the investigation of the state of the blood and
the blood-vessels in inflammation excited in the web of the bat’s wing,
I applied myself, in the first place, to the study of the distribution,
structure, and endowments of the arteries, capillaries and veins of the
part, and of the phenomena of the circulation in them.
I had not observed the circulation under the microscope long, before
I was struck with something peculiar in the flow of blood in the veins;
I therefore directed my attention to them, and discovered that they con-
tracted and dilated rythmically. Following the veins for some extent
in their course, I further discovered them to be provided with valves,
some of which completely opposed regurgitation of blood, others only
partially.
The cause of the peculiarity in the flow of blood in the veins was
thus no longer doubtful • but some continued observation was required
before I was able to make out exactly its mode of operation.
The act of contraction of the vein is manifested by progressive con-
striction of its caliber and increasing thickness of its wall ; the relaxa-
tion of the vessel, by a return to the former width of caliber and thick-
ness of wall.
The rythmical contractions and dilatations of the veins are, in the
natural state, continually going on; but sometimes with greater, some-
times with less rapidity, and sometimes to a greater, sometimes to a less
extent. The average number of contractions in a minute, I have found
to be ten. I have on some occasions counted only seven or eight, and
on other occasions as many as twelve or thirteen. Most usually, the
numbers were nine and eleven. The supervening dilatations take place
rather more quickly than the contraction. The amount of constriction
of one of the larger veins,—one about l-300th or l-400th of an inch in
width when dilated,—at each contraction of its walls, may be put down
at a fourth or fifth of its whole width when in a state of dilatation; I
have sometimes estimated it at nearly a third, sometimes at not more
than a sixth.
The contractions centrad and distad of a valve appeared to be simul-
taneous, as did also the dilatations.
The smaller veins, those of the first and second order, proceeding from
the radicals, contract, but not in a very marked manner, and are desti-
tute of valves.
During contraction, the flow of blood in the vein is accelerated. On
the cessation of the contraction, the flow is checked, and a tendency to
regurgitation of the blood takes place, which brings the valves into play.
Where the valves are perfect, ithe backward movement of the blood is at
once stopped by their closure; but where the valves are not complete,
the blood regurgitates more or less freely.* But this check to the on-
ward flow of the blood is usually only far a moment or two. Already,
even while the vein is in the act of again becoming dilated, the onward
flow of blood recommences and goes on, though comparatively slowly,
until dilatation is completed and contraction supervenes; whereupon
acceleration of the flew takes place as before.
* Sometimes, as for example, into a venous branch with an incomplete valve,
a retrograde flow of blood takes place from a large vein, at the moment this
latter is contracting and propelling its blood onwards.—May 7, 1832.
It is to be observed, that in determining the flow of blood in the veins
(the phenomena of which I have now described), the action of the heart
is concerned as well as the contractions of the veins themselves. It ap-
pears to be the heart’s action which maintains the onward flow of
blood during the dilatation of the vein, whilst it is the contraction of
the vein, coming in aid of the heart’s action, which causes the accele-
ration. Sometimes the vis a tergo is sufficient to keep up a pretty
steady flow in the veins, this being only accelerated at each contraction
of these vessels.
The check to the flow of blood in the veins takes place at the com-
pletion of the -contraction or commencement of the dilatation. The
number of checks observable in a minute, therefore, corresponds with
the number of ■.contractions. In one case, while an assistant marked the
time by a seconds’ watch, I observed that a complete valve checked the
tendency to regurgitation nine times in a minute; and on counting the
number of contractions of the same vessel, I found them also nine in a
minute. In another case, eleven checks and eleven contractions were
counted; and so on repeatedly. Though I quote these little experi-
ments, I would remark that, after some practice in the observation, the
eye is quite able to take in at one glance the succession and relations of
the two phenomena.
The valves of the veins are composed sometimes of but a single flap,
sometimes of two. In the situation of a valve, and centrad of the in-
sertion of its flaps, the veins .present the usual dilatations or sinuses
corresponding to the sinuses of Valsalva at the origin of the pulmonary
artery and aorta. • These sinuses are best seen when the valve happens
to present its flaps edgeways to the observer.
Valves are found close to the entrance of a large branch, but distad
of it. They are also found at intermediate parts of the veins. Tracing
the veins from radicles to trunks, the first valves I have noticed were at
the junction of the second order of veins to form the third.
In watching the circulation, it is interesting to observe the backward
eddy of blood-corpuscles into the sinuses of the valves, when the blood
issues from the narrow valvular opening into the wide part of the vein
beyond.
In structure, the valve3 are seen to be a reduplication of the clear
innermost coat of the vein, with sometimes a pretty evident layer of
fibrous tissue intervening.
Each vein is elosely accompanied by an artery, a nerve only inter-
vening. The average diameter of a vein is to that of its accompanying
artery as about 3 to 2.
The contractility of the arteries is altogether different in its nature
from that of the veins. It is conic contractility, not rythmical. On
the application of pressure over an artery, this vessel may be seen to
become constricted, sometimes even to temporary obliteration of its
caliber, and that uniformly throughout some extent of its course, both
above and below the point where the pressure was applied; or, the con-
striction is greater or less at intervals, so that the vessel presents a
varicose appearance. This tonic contraction of the arteries of the bat’s
wing does not take place quite so quickly as the same phenomenon in
the frog’s web, and, ordinarily, continues a longer time.
The pulsation of a vein so affects its accompanying artery as to push
the latter, as a whole, to and fro. That the movement of the artery
referred 'to is really owing to this cause, and not to any pulsation or
rythmical contraction and dilatation of its own walls, is evident from
this, that the movements are synchronous with the contractions and dila-
tations of the vein, and that both sides of the artery move in the same
direction, not approximating and receding from each other, so as to con-
strict or dilate the caliber, as in the case of the vein.
I have not been able to observe unequivocal evidences of tonic con-
tractility of veins in addition to their rythmical contractility. When
pressure is, at the same time, applied over the Vein as well as the artery,
the vein is not found to become tonically constricted in the same manner
as the artery, upward and downward. At the place where the vein was
pressed on, a mechanical indentation of its wall may perhaps be seen.
And, in addition to this, there may often be observed an appearance of
great and abrupt constriction. This appearance, however, is not owing
to contraction of the walls of the vein, but to a deposit of a viscid-looking
grayish granular lymph within the vessel at the place, obstructing its
channel and narrowing the stream of blood. On watching, I have seen
portions of this deposit detached and carried away by the stream of
blood, with corresponding enlargement of the channel, and again an
additional deposit with renewed narrowing of the stream. When the
pressure has been considerable, I have seen the vein become for a time
wholly obstructed by the deposit. A similar deposit of lymph takes
place in the artery. In one case, I observed that the artery,, at the
place pressed on, was actually not so much constricted as above and
below, though, on account of the narrowness of the stream of blood
from the presence of the lymphy deposit, it appears as much so at first
sight.
Having subjected the web to the galvanic influence from a single pair
of plates, I found all the smaller arteries of the part in a state of con-
siderable tonic constriction, but the larger arteries constricted in a less
degree. The effect of galvanism on the veins appeared to be to render
their rythmical contractions somewhat more brisk, they having been
previously rather languid. On cutting a vein across, I did not observe
tonic constriction of it, any more than in the frog.
After the application of a drop of vinum opii to the web, the veins
were found dilated as well as the arteries, and their rythmical contrac-
tions appeared to be suspended.
It has been stated, by an authority not liable to err, that, on
mechanical irritation, both artery and vein of the bat’s web gradu-
ally contract and close, and, by and by, dilate wider than before.
And, again, that in bats, contraction of veins is quite aswell marked as
that of arteries.
These statements, it will be observed, imply tonic contractility of the
veins.
Notwithstanding my attention has been repeatedly directed to the point,
I have not, as previously stated, been able to observe unequivocal evi-
dences of tonic contractility of veins, in addition to their rythmical con-
tractility. For this reason, I cannot help venturing on the supposition
that Mr. Paget must have made his statements either from a hasty and
imperfect observation of the proper rythmical contractions of theveins;
or, seeing that in rythmical contraction of the veins, the constriction is
never to closure, like that of the arteries, under some such misappre-
hension as to the nature of the vessel observed, as he certainly must
have labored under when he supposed that arteries and veins of the
second and third order open directly into each other without any inter-
medium of capillaries.
The arteries and their subdivisions anastomose freely with each other,
forming a network all through the web, the meshes of which go on to
diminish towards the free margin. Each artery, and each subdivision
of an artery, is closely accompanied by a vein; and these veins, like the
arteries they accompany, anastomose with each other. But it is to be
remarked, that nowhere do the arteries and veins directly communicate.
The only communication is the usual one through the medium of capil-
laries. The capillaries, the walls of which are destitute of contractility,
received the blood from small arterial twigs, which arise from the ar-
terial network, and return it to the venous radicles which open into cor-
responding veins. These arterial twigs, capillaries, and venous radicles,
.form networks within the meshes of the great vascular network, and a
looped network at a margin of the web.
The observations recorded in the preceding pages were made*princi-
pally with one-eighth of an inch object-glass, and the two lowest eye-
pieces, affording magnifying powers of 370 and 550 diameter.
The web of the wing was stretched out on the object-plate, wetted on
both sides with water, and covered with a thin plate of glass at the spot
to be examined.
Appendix to the foregoing Paper.
In consequence of the dark pigment in the cells of the epidermis of
the web of the bat’s wing, the structure of the vessels cannot be well
made out except by dissection.
A small piece of the web containing vessels being detached and dis-
posed in a drop of water, under the simple microscope, the two layers of
skin may be readily torn from each other with needles, and the artery
and vein, with their accompanying nerve, which lies between the two,
separated in one bundle.
In pieces cut out of a web which had been dried, the bundle of ves-
sels and nerve was, after tearing away the skiD, left surrounded by a
sheath of cellular and elastic fibres disposed longitudinally; but in
pieces cut out from the living web and directly examined, this sheath
was always detached along with the skin, and the vessels, with their ac-
companying nerve, at once laid bare.
Both artery and vein are seen to have a middle coat of circularly dis-
posed muscular fibres; but the appearance of the fibres is different in the
two vessels,
The fibres of the vein are about l-3600dths of an inch broad, pale,
grayish, semi-transparent, and granular-looking. In general aspect they
very much resemble the muscular fibres of the lymphatic hearts of the
frog. In none of the muscular fibres of the vein, however, did I detect
an unequivocal appearance of transverse marking.
The fibres of the middle coat of the artery are not so pale-looking as
those of the middle coat of the vein, are clearer, and exhibit a more
strongly marked contour.
Second Appendix.
From a microscopical examination of the bloodvessels and circulation
in the ears of the long-eared bat, I have ascertained that, different from
what I discovered to be the case in the wings, the veins of the ears are
unfurnished with valves, and are not endowed with rythmical contrac-
tility, and that the onward flow of blood in them is consequently uniform.
I ought, perhaps, to qualify the statement that the veins of the ears are
not endowed with rythmical contractility, by saying, that I think I
noticed a very slight tendency to it here and there in a vein, but so
slight as net to have the smallest effect on the flow of blood.
This observation regarding the ear of the bat illustrates how that the
heart’s action is sufficient of itself for the circulation of the blood in the
body generally; but that being sufficient for that only, the supplementary
force of rythmical contractility of veins, supported by the presence of
valves, is called forth to promote the flow of blood in the wings, which on
account of their extent, are, as regards their circulation, in a consider-
able degree, though not entirely, beyond the sphere of the heart’s in-
fluence.
I may take this opportunity to mention, that I have also found the
veins of the mesentery of the mouse destitute of rythmical contractility.
—Philos. Transact, 1852.