188 
MR. YOUATt’s VETERINARY LECTURES. 
ginning to enlarge. About the third lumbar vertebra the in¬ 
crease of size is very evident. These nerves, as soon as they 
escape from the canal, divide also into a superior and inferior 
branch; the first going to the muscles of the loins, while the 
inferior one, as I shall have to shew you when describing the 
muscles, is of great consequence. The inferior branch of the 
first lumbar nerve takes a long course over the transverse pro¬ 
cesses of the two next vertebrae to the iliacus, and along the 
muscles of the thigh, almost to the stifle. It has also, in com¬ 
mon with every nerve of the spine, communications with the 
nerves next before and behind, and with the great organic nerve. 
The second lumbar nerve is of more importance. It not only 
gives ramifications to the psoas and the iliacus, and extending 
even to the stifle, becomes the principal subcutaneous nerve of 
the thigh, but, passing through the abdominal ring, it dispenses 
nervous influence to the scrotum and testicle of the male, and 
the uterus, the pudenda, and the udder of the female. It even 
does more than this ; it helps to form one of the nerves of the 
hind extremity. Of these, then, I must next speak ; but it will 
be a hasty glance indeed that I can now take of them. 
The Nerves of the Hind Extremity .—These do not arise from 
one common nervous plexus as in the anterior extremity, and the 
branches that issue from which it is difficult or impossible to 
trace to their true nervous origin, but the formation of the ner¬ 
vous chords can be satisfactorily followed to distinct plexuses, 
referrible to particular nerves. 
The second lumbar nerve contributes a branch, and the third 
and fourth the greater part of their substance; and the fifth a 
considerable branch, to the formation of the crural nerve. Its 
principal distribution is to the rectus, and to the internal and 
external vastus; while no mean branches go to the iliacus, and 
the psoas magnus, and the pectineus, and then, becoming a sub¬ 
cutaneous nerve, it ramifies on the interior and forepart of the 
thigh and the leg, and may be traced as low as the fetlock. It 
accompanies the vena saphena in the greater part of its course, 
and should be remembered when we are bleeding from that vein. 
The third lumbar nerve sends a branch to form the obturator; 
the fourth more largely contributes, and a smaller branch is 
derived from the fifth. This nerve, after a short course, passes 
through the foramen magnum ischii, gives branches to the ob¬ 
turator muscle, to the pectineus, the triceps, and the gracilis. 
The fifth lumbar nerve detaches a branch to help to form the 
sciatic nerve; it receives a much larger one from the first sacral, 
and others from the second and third. This nerve quits the 
pelvis through the sacrosciatic ligament, passes between the 
