LANCASHIRE VETERINARY MEDICAL ASSOCIATION. 607 
pany with the occipital artery, and receives some branches from 
the cerebrum itself and from the cerebellum, and then, instead of 
uniting with the jugular high up, as do the auricular, the temporal, 
the parotideal, the submaxillary, and other veins, it receives com- 
munications from the thyroidean and laryngeal veins, and, accom- 
panying the course of the internal carotid artery, it at length unites 
itself with the external jugular vein, near its entrance into the 
thoracic cavity.” 
Professor Quain and others have described the veins in the 
human subject as having three coats — the external one, of condensed 
cellular tissue ; the central one, thinner and more pliant than that of 
the arteries, and composed of fibres, the greater part of which are 
longitudinal, and a few transverse. The internal coat consists of a 
thin shining membrane, and is continuous with that lining the 
heart. Veterinary authors mostly describe only two coats, a mus- 
cular and a membranous one, the elastic coat, according to some of 
them, being absent. 
On dissecting the jugular vein from the neck we find it sur- 
rounded by a considerable quantity of loose cellular membrane, 
which becomes more condensed as we approach the inner membrane. 
After removing this we can easily discover the texture of the vein 
to be composed of a vast number of minute threads or fibres as 
delicate as the finest silk or spider’s web, most of them being dis- 
posed in two layers longitudinally, the rest being circular and 
fibrous. The inner membrane on being cut across can easily be 
stripped off, and has the appearance, as in the human subject, of 
a thin, shining tunic lined with epithelial scales. The jugular vein 
is of immense strength. We are unable to break it by the united 
force of both hands, and, on separating longitudinally the delicate 
fibres of which the vessel is composed, we find each to be of great 
strength compared with its bulk. 
Within the jugular vein are reflexions or duplications of its 
lining membrane, called valves, but which Mr, Hunter says are of a 
tendinous and elastic nature, and of a different structure to the 
internal coat. I am inclined, however, to think that they are 
nothing more than fine duplicatures of the membrane, for I fancy 
that I have been enabled to separate them into two folds. 
In the human subject, I believe that there are two of these folds 
uniting to form one valve. Mr. Percivall says that in the horse 
there is commonly but one, sometimes two, at other times three. 
According to my experience there are generally two folds, sometimes 
three, and rarely but one. 
Some time ago I dissected from a horse’s neck the right or off 
side vein, from the breast to the bifurcation above. I found that 
there were three valves at the lower part of it, at intervals of nearly 
three inches from each other, and that there was a space of nearly 
a foot below the bifurcation without a valve. In another there 
were six valves in a space of twelve inches. 
I also dissected both the veins from the neck of a horse from the 
breast upwards. In one of them I found five valves. The four 
