592 ON TIIE DISEASES OF THE SPINAL CHORD 
its membranes, warrant this opinion; at the same time, I must 
acknowledge, that I have never met with this lesion ; and that in 
making such a presumption here, my object is to fix the atten¬ 
tion of veterinarians upon this important point of pathological 
anatomy. 
The Membranes of the spinal Marrow may inflame singularly 
or simultaneously. The last is the most frequent occurrence. 
These phlegmasia , the study of which has been long neglected, 
were formerly designated by the collective name of arachnitis; 
a denomination no longer admitted, and for the abolishment of 
which the motives will appear hereafter. 
Inflammation confined to the dura mater is very rare, and as 
vet has received no description in veterinary medicine. Indeed, 
it has been seen but little of in man, excepting in cases wherein 
the osseous parietes of the vertebral canal w^ere themselves 
diseased; and I have myself only one case to record of it in the 
horse, and that was the sequel of poll-evil. In this case, the 
pus had made its way to this membrane through a sinus running 
on the right side of the cervical ligament, betw een the atlas and 
den tat a. This latter vertebra had become slightly carious; and 
the dura mater, thickened and injected, presented a brownish 
surface covered w ith very foetid pus. 
I am as yet ignorant whether such effects follow virulent 
fistula: but it seems to me that the length of the spinous pro¬ 
cesses, and the thickness of the vertebrae and of the substance 
covering’ them, render such an alteration little likely to happen 
(if ever it does) in the regions of these maladies. 
The arachnoid membrane has long been regarded as the or¬ 
dinary seat of spinal phlegmasiae; though it appears to be well 
established at the present day that this membrane, of itself, is 
not susceptible of inflammatory action, and that all the morbid 
phenomena ascribed to it occur in the tissue underneath it. 
“ I know of no fact,” says M. Andral, “ proving that the 
arachnoid has ever been found injected, opaque, or thickened : 
these divers alterations constantly exist beneath it; therefore 
nothing is more incorrect than to aflix the denomination of 
arachnitis to inflammation w hich affects membranes immediately 
enveloping the marrow.” 
This opinion is likewise perfectly consonant with the re¬ 
searches of Beclard, and MM* Ribes and Ollivier, who give us 
to understand that neither in health nor disease has any vessel 
ever been discovered in the arachnoid. 
Despite, however, of the judicious reflections of M. Andral 
and the accurate and important investigations just cited, it does 
appear to me surprising that we should deny the possibility of 
