414 MR. ST. GEORGE MIVART AND DR. .1. MURIE [June 20, 



gastrocnemius, its tendon becomes superficial to that muscle ; wrap- 

 ping round it, and proceeding beneath the tuberosity of the os calcis, 

 it becomes continuous with the plantar fascia, and forms the perfo- 

 rated tendons of the three digits (figs. 4 & 5, P.). In the Rabbit 

 and Hare it terminates in four tendons ; but the Guinea-pig has 

 three, as in the Agouti. 



Prof. Huxley, in his Hunterian Lecture, 20th March, 1865, said, 

 " The extensor muscles of the leg in the Rabbit are inversely de- 

 veloped ; for the flexor brevis is represented by a muscle which arises 

 in the leg — namely the plantaris, which springs, as usual, from the 

 outer condyle, wrapped up in the heads of the gastrocnemius and 

 soleus, and it is relatively immense. It ends in a tendon which 

 spreads on the pulley-like end of the calcaneum, and divides into 

 four perforated tendons, thus replacing the flexor brevis, as in Da- 

 sypus sexcinctus." 



The soleus has origin from the external side of the head of the 

 tibia. Its tendon has an insertion in common with the tendo Achillis 

 into the os calcis (figs. 4 & 5, So.). 



Alike in the Guinea-pig ; but in the Hare the tendon of insertion 

 continues perfectly separate from that of the gastrocnemius to the 

 very os calcis itself. 



The popliteus comes by a strong tendon from the external condyle 

 of the femur. It is inserted as usual, but lower down, occupying as 

 much as two-fifths of the tibia, which it also does in the Guinea-pig, 

 the Hare, and the Rabbit. 



The flexor longus digitorum is, comparatively speaking, a small 

 muscle, certainly much less in volume than the flexor longus hallu- 

 cis is in Hyrax*. It arises by a few delicate fibres from the head 

 of the fibula, but mainly from the back of the tibia, except the part 

 covered by the popliteus. It becomes tendinous superficially above 

 the middle of the leg, and the tendon, as it becomes round in form 

 at the ankle, glides through a groove behind the internal malleolus 

 and joins in the sole of the foot the broader tendon of the flexor 

 longus hallucis ; but the tendon of the flexor longus digitorum is 

 seen of itself to form the principal part of the tendon going to the 

 index (figs. 4 & 5, F. I. d.). In the Guinea-pig the conditions are 

 the same. In the Hare this muscle is intimately connected with 

 the flexor longus hallucis, both in the fleshy bellies and in the ten- 

 dons ; but it appears to supply mainly the perforating tendons of the 

 index, middle, and fifth digits. 



The flexor longus hallucis, as in Hi/raxf, is much larger than the 

 flexor longus digitorum. It has origin from the upper two-thirds 

 of the fibula and the interosseous membrane. Below, it forms a very 

 large tendon, which, passing in a deep groove at the back of the 

 tibia, unites with the preceding muscle, and terminates as the per- 

 forating tendons, forming, however, almost exclusively those of the 

 third and fourth digits (figs. 4 & 5, F. I. h.). 



The same in the Guinea-pig. In the Hare it is, as before said, 

 closely united with the flexor longus digitorum, both in its belly and 

 * P. Z. S. 1865j p. 350. t Ibid. 



