THE 
VETERINARIAN. 
VOL. VII, No. 76 .] APRIL, 1834. [New Series, No. 16 . 
MR. YOUATT’S V ETE RI N A R Y LE CTU R E S, 
DELIVERED AT THE UNIVERSITY OF LONDON. 
LECTURE XL. 
The Membranes of the Spinal Marrow—The Origins and Dis- 
n tribution of the Spinal Nerves . 
OF the compound spinal nerves, of which I spoke in my last 
lecture, there are thirty-six pairs. I find the first of them at the 
very commencement of the medulla spinalis; it is the sub-occipi¬ 
tal, or, more properly, the frst cervical nerve. It arises in the 
way that I have already described from the lateral furrow on the 
superior and inferior surfaces of the spinal chord ; the fasciculi 
from the superior surface converging, and forming a ganglion— 
the fasciculi from the lower surface converging, uniting with the 
other beyond the ganglion, and the two trunks entering into one 
sheath, and forming one inseparable compound nerve. 
The Membranes of the Spinal Nerves . The Dura Mater .— 
There are, however, some material differences between this com¬ 
pound nerve and the only one, the fifth, which I have yet exa¬ 
mined : and, glancing over the spinal canal, we perceive that these 
differences are common to all the nerves of the spine. We can 
trace, on the spinal chord, the membranes which envelope the 
brain ; but there are some peculiarities about them which de¬ 
serve our observation. 
Within the cranium the dura mater adheres to the bone. It is 
the internal periosteum ; it continues to line the cavity until we 
arrive at the foramen magnum ; it adheres closely to the edge of 
the foramen magnum, and also to the upper edge of the foramen 
in the atlas, which is the commencement of the spinal canal. 
That edge, however, being passed, it is no longer the internal 
periosteum of the bone : the spinal canal has a periosteum of its 
own, and a very singular and effectual one—a ligamentous as 
well as membranous one. The dura mater is perfectly detached 
from it, but continues to envelop and to protect the prolongation 
of the brain, and in a manner best suited to its altered situation 
vol. vn. B b 
