ON DORSO-LUMBAR SPRAIN IN THE HORSE. 45 
surfaces themselves: this, on the contrary, is an exceedingly 
rare occurrence—one, therefore, that will require especial notice. 
A. The articulatory surfaces are sometimes completely de¬ 
nuded, deprived of the intervertebral discs. In making a sec¬ 
tion of the spine through its axis, cutting through the middle of 
the osseous mass in which in which they are enveloped, we 
find the articulatory surfaces smooth, and in their proper posi¬ 
tion and relative distance, with their intervertebral discs per¬ 
fectly free. The articulatory surfaces (ball and socket) present 
there the same appearance as the long bones after maceration, 
when they have been deprived of their diarthrodial cartilaginous 
plates. 
B. Sometimes the intervertebral discs are evidently stretched, 
or else they are partially destroyed around their circumference. 
In this state they exhibit a yellow tinge of more or less inten¬ 
sity, sometimes slightly greenish; while the destroyed edges, in 
contact at the time, are perfectly smooth, as though they had 
all the time been rubbed one against the other. At another 
time, the intervertebral disc has been completely ruptured, pre¬ 
senting then, upon the entire ball and corresponding socket, 
the characters beforementioned. 
C. In other animals in which rupture of the disc had taken 
place, and where there had been stretching of the superior and 
inferior common vertebral ligaments, I have found a sort of 
ulceration, of more or less extent, of the articulatory surfaces 
and surrounding parts of the vertebrae, several spinal abscesses, 
internal and external, &c. I have reported two cases of this 
description, and we shall see to what extent under such circum¬ 
stances they may be multiplied. 
D. I now come to speak of those cases of pathological ana¬ 
tomy on which Rigot lias given an opinion, perhaps too abso¬ 
lute, in the following passage :—Ossification or change into bone 
ot the intervertebral fibro-cartilages is much more rare than is 
generally believed, since, in the immense majority of the cases 
of intervertebral anchylosis which I have had occasion to ob¬ 
serve, I have never seen these bodies so changed. 
That this is an exceeding rare occurrence, is true ; at the 
same time 1 have met with some instances, and I have recorded 
two or three ol them, one between the second and third cervical 
vertebrae, another between the second and third dorsal ver¬ 
tebrae. In this same spine are likewise coalitions, almost com¬ 
plete, between the second and third, fifth and sixth, and sixth 
and seventh vertebrae; and it is abundantly evident, as I said 
in another place, that ossification proceeds on the articulatory 
surlaces from the circumference to the centre. 
In man, ossification of the vertebrae, or veritable anchylosis 
of them, though rare, is more frequent, perhaps, than in domestic 
animals, owing to the greater duration of life, and probablv also 
to difference of station. Some splendid examples of it are to 
