264 Rev. S. Haughton on the Muscular Mechanism 



partly by a muscular slip into the middle of the vastus externus. 

 (c) The caudal portion of this muscle is inserted into the pos- 

 terior border of the tendon (a), near the knee. The weight of 

 the whole muscle is 46| oz. 



2. The glutseus medius has the origin marked in fig. I., on 

 the surface of the ilium, and is inserted in the small pit on the 

 outside of the head of the feniur (PI. VII. fig. II.), and rather 

 behind. Its weight is 13;^ oz. 



3. The glutseus minimus in the Ostrich is correctly so named, 

 for it is a very small muscle ; it arises from a thin line on the 

 ilium, If inch in length, shown in fig. I., just behind the origin 

 of the iliacus, and is inserted, with the opponens quadrato 

 femoris, below the great trochanter, on the front of the femur 

 (fig. II.). Its weight is 1 oz. 



4. The biceps femoris has a bony origin below that of the 

 glutseus maximus on the ilium, and lies along the entire surface 

 of the bone, between that muscle and the semimembranosus 

 (fig. I.) ; it is inserted into the tubercle in the middle of the 

 fibula (fig. v.). Its weight is 41 J oz. 



5. The semitendinosus takes its origin from the bony promi- 

 nence of the posterior extremity of the ilium, from the tuber 

 ischii and the membrane that joins these two points (fig. I.), and 

 is inserted into the inner margin of the upper and posterior 

 surface of the tibia. Its weight is 14 oz. 



A remarkable accessory muscle arises from the insertion of 

 the adductor magnus (fig. II.) in the femur, and is fastened into 

 the tendon of the semitendinosus near its insertion into the 

 tibia; this accessory muscle weighs 1 oz., and runs nearly at 

 right angles to the tendon of the semitendinosus. Its action is 

 to lift and guide the tendon, so as to increase the force of the 

 semitendinosus in propelling the body forwards when the foot 

 is fixed. The mechanical use of this muscle is similar to that 

 of the accessorius flexori digitorum longo in the sole of the 

 human foot. 



6. The semimembranosus has its origin on the ilium, below 

 the biceps, as shown in fig. I., and it is inserted in a line com- 

 mencing at the top of the linea aspera of the femur (figs. II., III.), 

 and extending to the fascia of the thigh down as far as the inner 

 side of the knee. Its weight is 17 oz. 



The similarity of its use to that of the glutseus (1) is shown 

 by the circumstance that it sends a slip (IJ oz.) backwards to 

 the sides of the first two or three caudal vertebra?, which must 

 be regarded as an additional agitator caudse. 



7, 8. The vastus externus is composed of two parts : — (l)having 

 an inverted T-shaped origin from the great trochanter, between 

 the insertions of the glutseus medius and minimus (fig. 11.) ; it is 



