1894.] 



NATURAL, SCIENCES OF PHILADELPHIA. 



179 



Now these people are right in attributing to the flexor metatarsi 

 tendon the function of opposing itself to the flexion of the femur, and 

 wrong only in making this function auxiliary to muscular forces, 

 which are not called upon to sustain weight, and which if called upon 

 in the usual way would start progression. 



"To fulfil the function of sustentation," says Chauveau, "the foot 

 would have to be held by the gastrocnemii muscles w^hich," he says, 

 "tend to flex the femur on the tibia." 



My experiment with the dead horse, the muscular fibres having 

 been cut away, shows that the perforatus and perforans tendons 

 maintain the foot, without the assistance of the gastrocnemius muscle, 

 which does not flex the former upon the tibia, but extends it, as I 

 have shown before. I mistrust entirely the accuracy of Chauveau's 

 observation as to the effect of cutting the tendon in the living horse. 

 The severance of this mighty cord in the dead horse causes instant 

 collapse. I suspeect that in Chauveau's experiment the cord was 



but imperfectly cut ; or, it may be, that by an 

 extraordinary co-ordination of muscular effort 

 the poor beast still stood for a short time previ- 

 ous to its final destruction, but it is inconceiv- 

 able to me that a trained and unprejudiced ob- 

 server should detect no change in the appear- 

 ance of the animal upon the destruction of such 

 a great part of the mechanism. 



I shall close this communication with another 

 beautiful example of muscular differential ac- 

 tion. In the arm of the horse (fig. 6) we have 

 two principal muscles, the biceps in front of the 

 bone and the triceps behind. The biceps flexor 

 radialis surrounds the tendon which I have 

 drawn in heavy black line, and takes a long 

 leverage above, at the shoulder joint, and a 

 very short one below, on the radius. The long 

 head of the triceps arises from the axillary 

 border of the scapula, and is inserted into the 

 olecranon. The olecranon is set far back and above the elbow joint, 

 to afford to the triceps a greater leverage below than above, reversing 

 the condition of the biceps. These two muscles, during the act of 

 progression, form a complete circuit of strain. The action of the 



Fig. 6. 



