i62 THE SURGICAL ANATOMY OF THE HORSE 



ship to the external iUac artery, some abnormal dilation of the artery, 

 such as the presence of an aneurism, would exert a considerable amount 

 of pressure upon the nerve, and might possibly bring about paralysis. 

 Shortly afterwards an opportunity was presented to make observations 

 on the point. A pony was purchased for dissection which was a typical 

 case of crural paralysis. From the meagre history which it was possible 

 to glean, the pony had not been the subject of hasmoglobinuria. Upon 

 dissecting the sublumbar region it was found that there was a gradual 

 contraction of the first two and a half inches of the external iliac artery, 

 and this part was followed by a distended portion almost two inches 

 in length, and possessing a diameter approximately two and a half times 

 that of the remainder of the vessel. Upon making an incision into the 

 vessel the distended portion was found to contain a quantity of dis- 

 integrated blood adherent to the vessel's wall, but the lumen of the 

 vessel was not obliterated, and the thrombus was therefore parietal. 

 There is little doubt in this case that the continuous pressure of the 

 distended portion of the vessel upon the nerve interfered with the 

 functional activity of the latter {Veterinary Record, July 27, 1907). 

 Although the author has not had the good fortune to come across other 

 cases of this kind in the meantime, from the anatomical relationship 

 which the structures bear to one another he is under the impression that 

 this case provides what is possibly an explanation of quite a number of 

 the obscure cases of this disease to which reference has already been 

 made. 



Regarding the symptoms which are presented, there is inability on 

 the part of the muscles supplied by this nerve. This inability at first 

 may be but slight, and is evident only in a want of the former freedom 

 in extending the stifle joint. Later on the animal becomes unable to fix 

 the joint, and weight cannot be supported by the affected limb. Sensation 

 is lost on the inner aspect of the thigh. The external and internal vasti, 

 together with the two recti muscles, will now be observed to be losing 

 their normal bulk, and later marked atrophy of these muscles will be 



