628 MR. A. H. GARROD ON [Julie 17, 



Tensor fascia. — This is the superficial muscle of the outside of the 

 thigh, covering the femur. It is flat and triangular in shape, and 

 arises as a membranous expansion which covers the gluteus ii., from 

 the lower two thirds of the posterior border of the iliac fossa in which 

 that muscle is situated, and from the fibrous septum which separates 

 that muscle from the gluteus iii. Further down it has origin also 

 from the whole length of the ridge which separates the postacetabular 

 area from the external lateral surface of the ischium, and which may 

 be termed the postacetabular ridge, as well as from the posterior 

 border of the ischium, as far forwards as its junction with the pubis, 

 being here slightly overlapped by the semitendinosus. The fibres 

 converge towards the knee ; and the deep portion of the muscle blends 

 in its course with the vastus externus, together with which it con- 

 tinues forward to become part of the broad thin tendon which covers 

 the knee and is inserted in the front of the tibia-head, the patella 

 being situated in it, together with the long, slender, and flat tendon 

 of the ambiens muscle, which is situated below it, running obliquely 

 from inside aud above, outwards and downwards. In many birds, as 

 the Falconidae aud Psittaci, this muscle does not extend below the 

 level of the femur, but ends inferiorly by blending with the vastus 

 externus ; and consequently, where such is the case, it evidently 

 cannot, as it does otherwise, cover any of the flexors of the leg. In the 

 Bucerotidce it is entirely absent. Whether this postacetabular portion 

 of the tensor fasciae is present or absent has some bearing on classifi- 

 cation, as in the different families it is a very constant feature. 



Biceps cruris. — The anterior portion of this muscle may be seen 

 in the Fowl's leg before the tensor fasciae has been removed, just 

 below it, near its insertion. This muscle is mostly covered by the 

 tensor fasciae, arising from the upper three fourths of the postaceta- 

 bular ridge, just in front of the origin of that muscle. Its fibres 

 converge to form a round tendon, which in the outer side of the 

 popliteal region is bent sharply downwards by passing through a 

 tendinous sling which arises from the lower end of the femur, to be 

 inserted on a prominence on the outer side of the fibula, about half- 

 way down the leg. In the loop above this tendon, and consequently 

 quite out of the way of compressing forces, one of the nerves to 

 the leg and foot is continued. In one or two birds, as Phaethon, 

 the biceps does not pass through any loop, but is inserted directly 

 by a broad flat tendon into the upper part of the fibula. 



Semitendinosus. — This flat ribbon muscle runs nearly parallel with 

 the lower fibres of the biceps, just below it. Its origin is mostly 

 from the tip of the transverse process of the first free coccygeal ver- 

 tebra, and from the fibrous membrane between it and the inferior 

 Dorder of the ilium. Near its origin it, being superficial, curves over 

 the posterior inferior angle of the ilium, and covers the inferior fibres 

 of origin of the tensor fasciae, running upwards and forwards towards 

 the inner side of the head of the tibia, and so getting covered an- 

 teriorly by the inserted end of the biceps. A rhomboidal sheet of 

 muscle, arising from the anterior eud of the liuea aspera, descends to 

 form an accessory head to this muscle, joining it anteriorly, on its 

 outer side, by an oblique tendinous raphe, which continues down the 



