[ >31 ] 
X. Discovery that the P'eins of the Bat's JVing {which are furnished with valves) 
are endowed with rythmical contractility , and that the onward flow of blood is 
accelerated by each contraction. By T. Wharton Jones, F.R.S., Fullerian Pro- 
fessor of Physiology in the Royal Institution of Great Britain, Ophthalmic 
Surgeon to University College Hospital, and Corresponding Member of the Society 
of Biology of Paris, &^c. 8 ^c. 
Received November 20, 1851. — Read February 5, 1852. 
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 ; 1 therefore directed my 
attention to them, and discovered that they contracted 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 constriction of its 
caliber and increasing thickness of its wall ; the relaxation of the vessel, by a return 
to the former width of caliber and thickness of wall. 
The rythmical contractions and dilatations of thg veins are, in the natural state, 
continually going on ; but sometimes with greater, sometimes with less rapidity, and 
sometimes to a greater, sometimes to a less extent. The average number of con- 
tractions 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 contractions. The amount of constriction of one of 
the larger veins — one about 3-^dth or ^^dth 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, some- 
times at not more than a sixth. 
s 2 
