882 DR. C. F. SONNTAG ON THE MYOLOGY 



membranosus, and from the caudal vei-tebrse, the two parts being 

 separate. No femoral head is present. The ischial part expands 

 and becomes fan-shaped ; it is inserted into the fascia over the 

 fibula in the proximal two-thirds of the leg. The caudal part is 

 at first superficial to the ischial part, but winds round it and 

 divides into two portions. One of these fuses with the ischial 

 part. The other fuses with semitendinosus, and then is inserted 

 into the middle of the subcutaneous mesial surface of the tibia. 

 The conditions present differ in several respects from Cunningham's 

 account of the muscle in Phalangista maculata. In Pseudochirus 

 the conditions are essentially similar to those in Phalanger. In 

 Phascolomys it arises entirely from the ischial tuberosity along 

 with semimembranosus, and it is inserted into the fascia over the 

 proximal third of the fibula, and into the bone itself, but it is not 

 divisible into two parts as in the Phalangerid?e. ISTo femoral 

 head is present. Its insertion is less than in Phascolarctos and 

 the Phalangeridse. 



No bicipiti accessorius is present in any of these animals. 



Semimembranosus (text-fig. 40) : — In all forms it is muscular 

 from origin to insertion, and there is a vaiiable amount of union 

 to the biceps ; and the course in all is from the tuber ischii to the 

 mesial aspect of the leg. In Phascolarctos it is inserted into the 

 quadriceps tendon, internal tuberosity of the tibia, and the fascia 

 of the leg ; and some of the fibres fuse with the triceps adductor 

 femoris. In Phalanger the insertion is moved farther distally. 

 It avoids the adductor and quadriceps, passes under the internal 

 lateral ligament of the knee, and is attached to the anterior 

 tuberosity of the tibia. And, as Cunningham (2) pointed out in 

 Phalangista maculata, it must rotate the leg on the thigh and act 

 as a powerful flexor. In Phascolomys it is inserted into the 

 mesial aspect of the head of the tibia. 



Semitendinosus (text-fig. 40) : — In Phalanger it is inserted into 

 a narrow strip of the middle of the ventral border of the shaft of 

 the tibia. But Cunningham (3) described it as going to the 

 mesial surface of the bone in Phalangista maculata. In Phasco- 

 larctos it is inserted into the mesial aspect of the tibia at the level 

 of the prominent tubercle on the anterior (ventral) border. In 

 Phascolomys it runs to the mesial border of the tibia in its middle 

 third. No tendinous insci'iption is present in any of these 

 Marsupialia. The muscle fuses with the biceps in Phalanger and 

 Phascolomys, but is quite free in Phascolarctos. But Macalister 

 (18) described it as free from other muscles in Phascolomys and 

 Phalanger. 



Gastrocnemius : — In Phalanger., as in Phalangista maculata, the 

 two parts from origin to insertion are quite separate. The inner 

 head arises from the back of the internal condyle of the femur, 

 and its tendon is inserted into the tuberosity of the os calcis. The 

 outer head arises from the proximal sixth of the shaft of the 

 fibula and from the intermuscular membrane between it and 

 the peronei ; its tendon is inserted into the tuberosity of the 



