186 
EMBOLISM OF ILIAC ARTERIES. 
salient feature, and was unquestionably a legitimate rssult of 
defective nutrition. As long as the mare was kept in a state 
of quietude, or even when having moderate walking exercise, 
the collateral circulation, assisted probably by a small channel 
in the embol, was adequate to support the limited demand 
of muscular power; but when exertion as in trotting was 
called forth, sufficient blood was not furnished to support 
the nerves conveying the impression of the will to the 
muscles ; or, it may be, to enable the muscles themselves to 
respond to a stimulus provided the nerves were in a fit state 
to convey the impression produced by that stimulus. 
Another well-marked symptom, referable to the perverted 
circulation, was coldness of the extremities. 
What still remains to be described is the manner in 
which the obstructed arteries of the hind extremities gave 
rise to a firm and persistent contraction of the muscles of 
the quarters, back, abdomen, and ribs. 
Firstly, then, it may be that the mare, finding the muscles 
of the hind legs unable to fulfil their ordinary office, called 
into action, through the stimulus of the will, other muscles 
to act as substitutes for those already incapacitated. But I 
hold that this rigid contraction of the muscles was involun- 
tary, for it continued as long as the circulation was accele- 
rated, and even when the mare had assumed the recumbent 
position, a time when she could scarcely be expected to be 
exercising her volition on muscles then painfully contracted. 
Now, in endeavouring to explain the manner in which this 
rigid contraction was brought about, I assume that the strong 
rapid current of blood in the posterior aorta, occasioned by 
the heart's increased action due to exertion, meeting with 
resistance from the external iliac artery on one side, and the 
internal iliac on the other, caused an inordinate quantity of 
blood to be driven with increased force into and through the 
vessels of the spinal cord ; produced congestion of that ner- 
vous centre, which congestion acting as an irritant or central 
stimulus, gave rise to contraction of those muscles abundantly 
supplied with blood, and that received their motor nerves 
fram the stimulated parts of the spinal cord. 
This case is necessarily incomplete from the absence of a 
post-mortem examination ; still, I have thought it sufficiently 
interesting and important to be worthy of record. The mare 
is still living. 
[As Mr. Little suggests, this case, though interesting, is 
incomplete ; but should an opportunity of making a post- 
mortem examination occur, we do not doubt that Mr. Little 
will take advantage of it and publish the result. — Eds.] 
