VARIETIES AND CAUSES OP STRINGHALT. 1023 



causes may at times be active, though, as a rule, neither can be 

 clinically identified. Amongst mechanical causes — for we may 

 also term the first variety mechanical — changes in the extensor 

 pedis tendon, the fascia of the thigh, and the patella or its ligaments 

 deserve special attention. Even though Siedamgrotzky's attempt 

 to produce contraction by exposing the peroneus tendon, and thrusting 

 a piece of wood under it, gave negative results, yet numerous 

 experiments show that section of this tendon often removes string- 

 halt. But the fact that it sometimes fails shows that stringhalt 

 is not due to a single cause. Amongst the others must be included 

 contraction of the fascia of the thigh, referred to by Dieckerhoff , of the 

 tensor vaginae femoris, much spoken of by Hertwig, and of the inner 

 lateral ligament of the patella, mentioned by Bassi. Moller has had 

 no practical experience of the last, though he has repeatedly seen 

 stringhalt-like movement in horses suffering from habitual upward 

 luxation of the patella, and as in these cases the form of the surface 

 of the trochlea of the femur possibly plays a certain part, it seems 

 possible that division of the inner lateral ligament of the patella 

 might prove of service. Moller several times divided the fascia 

 of the thigh when section of the peroneus tendon had proved insufficient, 

 but rarely saw real improvement. When section of the tendon 

 was unsuccessful, that of the fascia always failed. Sometimes these 

 three structures may be divided without affording relief, in which 

 case the condition is probably reflex, and either resembles chorea 

 minor of man, or is due to disturbance in the co-ordination of move- 

 ment, i.e., ataxia (see " Paralysis of the Hind Extremities "). 



The results of peripheral irritation chiefly affect the flexor muscles, 

 because the extensors act principally whilst weight is thrown on the 

 limb, and their contraction is therefore more easily controlled. 

 Possibly the central disturbance manifested by the affection of certain 

 groups of muscles may sometimes be of a secondary character, the 

 peripheral irritation in time causing changes in the central nervous 

 mass. At any rate, temporary disease of parts removed from the 

 centre sometimes produces chronic stringhalt. Thus, after injuries 

 to the foot, such as pricks, treads, or laminitis, wounds of the hock, 

 fractures of the external angle of the ilium, or even after the application 

 of a blister or the actual cautery, one sometimes sees stringhalt, 

 which continues despite removal of the original irritation. Ascheberg 

 saw stringhalt result from tetanus. In such cases one might imagine 

 that the peripheral irritation had produced permanent interference 

 with innervation, and that the oft-quoted dictum of Jordanus Ruff us, 

 " Cessante causa cessat effectus" no longer applied. Dollar is of 



