CONTRACTILITY OF VEINS OF THE BAT. 
135 
one-eighth of an inch object-glass, and the two lowest eyepieces, affording magnifying 
powers of 370 and 550 diameters. 
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. 
Received December 11, 1851, — Read February 5, 1852. 
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 disposed 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 vessels and nerve 
was, after tearing away the skin, left surrounded by a sheath of cellular and elastic 
fibres disposed longitudinally ; but in pieces cutout from the living web and directly 
examined, this sheath was always detached along with the skin, and the vessels with 
their accompanying nerve at once laid bare (see Plate IV. fig. 5.). 
Both artery and vein are seen to have a middle coat of circularly disposed muscular 
fibres ; but the appearance of the fibres is different in the two vessels. 
The fibres of the vein are about y-gJg^dths of an inch broad, pale, grayish, semitrans- 
parent and granular-looking. In general aspect they very much resemble the mus- 
cular 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. 
Received May 10, — Read May 13, 1852. 
From a microscopical examination of the blood-vessels and circulation in the ears 
of tlie 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 contractility, and that the onward flow of blood in 
them is consequently uniform. I ought, perhaps, to qualify the statement that the 
veins of the ear 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 
not 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 con- 
