PARASITES—TUMORS. 279 
a wooden wedge between the metatarsus and the tendon of the lateral ex- 
tensor of the phalanges so as to stretch it. L. Lafosse considers it only 
a perversion of the muscular contraction. He says: “It is only a spas- 
modic contraction of the flexor muscles of the metatarsus. We have re- 
moved it several timés by the section of one or several of these muscles, 
which we have never found in that state of permanent retraction considered 
by Belgian veterinarians as cause of springhalt.’”” Hertwig locates the af- 
ection in the excessive tension of the elevators of the thigh, and recom- 
mends for it the section of the fascia ata. Gunther thought it to be due 
toan insufficiency of action in the muscles of the croup. Delafond be- 
lieved it a diseased stretching of the tibial aponeurosis, an opinion recently 
accepted by Dieckerhoff. After a minute study of the part played by 
aponeurosis in locomotion the Berlin professor has pretended that spring- 
halt is due to the shortening of the tibial aponeurosis, followed in time by 
the atrophy of the dexor muscles of the metatarsus. In an interesting 
paper Wolf sustained the theory of Dieckerhoff. Orillard believes spring- 
halt related to laceration of the muscles-of the gluteal and posterior tibial 
regions or to partial ruptures of the cord of the hock. 
The nervous etiology of springhalt has from the start counted many 
advocates. We have already named Lafosse and Bourgelat. Youatt and 
Spooner attribute it to the lesions of the great sciatic nerve, which “ irritates 
too violently ” the flexor muscles. Perciwall attributed it to disordered 
muscular contractions brought on by affection of the cord or the nerves 
of the hind leg. At post-mortem examinations of animals thus affected 
Renner has always found a chronic inflammation of the great sciatic 
nerve, and for him the spasmodic contractions of the flexor muscles of 
the tibia and hock must be due to this chronic neuritis. Vachetta, taking 
the theory of Renner anew, gives the facts a different interpretation. For 
him the paresis of the muscles supplied by the great sciatic nerve (biceps 
femoris, semi-tendinosus) gives rise to a predominance of action in the 
anterior muscles of the leg. Merle, Rousseau and Comény think that 
springhalt is due to medullary lesions. 
Some authors attribute it to foot alterations. Watrin has advanced a 
theory that Weber, Lavalard and Montagnac accept for certain cases. 
He says: “By the action of the tendons of the flexor of the digits the 
flexion of the hock forcibly carries with itself that of the phalanges; then 
let us suppose that for any cause the flexion of the phalanges meets with 
an obstacle, the animal will make an effort to overcome it; if this dis- 
appears suddenly by reason of the force used, the flexion will be exaggerated,. 
and in some cases springhalt will appear.” Watrin especially suspects 
the contraction of the external quarter of the foot and the rolling in 
of the corresponding cartilage, which, hitting against the posterior face of 
