1903.] THE MUSCLES OF THE UXGULATA. 281 



instance, with the exception of Hvrax, we haA^e met with in the 

 whole order of any trace of a fleshy flexor hrevis digitorum. 

 Slips are given off which act as flexores perforati to all four 

 digits. In the Suidte (4, 7, 11, 12, 13, 14) the fleshy belly in 

 the calf is also fairly large and is wrapped up in the outer head 

 of the gastrocnemius ; passing round the tuber calcis its tendon 

 gains the sole and usually divides into three slips for the index, 

 medius, and annularis digits, though occasionally (12) it goes to 

 all four digits.' In the rest of the Artiodactyla its fleshy belly 

 is much smaller, and its tendon, after passing round the pulley- 

 like surface on the back of the tuberosity of the calcaneum, enters 

 the sole and gives off a loop from its deep surface which surrounds 

 the flexores tibialis et fibularis, then the tendon divides for the 

 medius and annularis digits, and each slip acts as a flexor per- 

 foratus before being inserted into the middle phalanx. In the 

 Ox especially the perforation of the tendon takes up a good deal 

 of its length, and a section through the perforans and perforatus 

 tendons shows the former enclosed by a complete ring of the latter. 



In Dorcatherium (23) Chatin describes tendons to all four 

 digits. In the Perissodactyla the muscle rises from the supra- 

 condylar fossa and passes to the middle phalanges of all the toes, 

 i. e. one in the Horse and three in the Rhinoceros and Tapir, 

 In the Subiuigulata, Hyrax (74, 75) has a fleshy flexor brevis 

 developed in the sole. The nerve-supply is always the internal 

 popliteal. 



Popliieus. — There is but little of special interest about this 

 muscle in the Ungulata ; it rises as usual from the outer surface of 

 the external condyle and is inserted into the upper quarter or third 

 of the posterior surface of the tibia. As a rule no sesamoid is 

 developed in its tendon, though we found one in ovir Tapir. The 

 anterior tibial artery apparently always passes in front of the 

 mviscle. With regard to the nerve-supply the Duiker-bok (54) 

 and Harnessed Antelope (55) have a branch from the internal 

 popliteal entering the muscle at its lower border but not curving 

 round that border as in Man, in addition there are two or three 

 smaller branches entering the posterior surface. 



Flexor fihtdaris {Flexor longus hallucis of human anatomy). — 

 This, except in the Camel and Elephant, is much lai-ger than the 

 flexor tibialis, and rises from the posterior surface of the tibia a 

 little lower than the latter ; it winds round the internal malleolus 

 and is soon afterwards joined by the flexor tibialis ; it then 

 divides into a variable number of tendons which pierce those of the 

 flexor brevis digitorum or continuation of the plantaris, and are 

 inserted into the terminal phalanges. In the Hippopotamidse, 

 Suidse, and I)orcathe7-ium there are four tendons, in the other 

 Artiodactyla only two ; in the Rhinoceros, Tapir, and Hyrax 

 three, in the Horse one ; and in the Elephant the combined 

 flexores tibialis et fibularis give tendons to all five digits, though 

 the chief contribution is from the tibialis. It is always supplied 

 by the posterior tibial nei-ve. 



