378 THE MUSCLES OF THE DOG 



tachment to the last rib. The anterior part of the aponeurosis divides into two 

 layers, which concur in the formation of the internal and external sheaths of the rec- 

 tus. 



The rectus abdominis is attached by a long tendon on the first five or six costal 

 cartilages, and by fieshy fibers on the xiphoid cartilage. It usually has five ten- 

 dinous inscriptions. The two recti diverge very gradually in front, so that they are 

 about half an inch (ca. 1 cm.) apart in the xiphoid region. 



The transversus abdominis presents no special features except that the poste- 

 rior part of its aponeurosis splits into two layers which include the rectus between 

 them. 



Muscles of the Pelvic Limb 



The psoas minor arises from the bodies of the last three or four thoracic and 

 first three or four lumbar vertebrae, and is inserted into the iliopectineal line. Its 

 anterior part blends with the quadratus lumborum. 



The psoas major is relatively small and short; it arises from the last three or 

 four lumbar vertebrae. 



The lateral head of the iliacus is small, while the medial head is large and fuses 

 with the psoas major to constitute an ilio-psoas. 



The quadratus limiborum is well developed, and extends laterally beyond the 

 edge of the ilio-psoas. It arises from the last three or four thoracic vertebrae in 

 common with the psoas minor, and from the last rib and the lumbar transverse 

 processes, and ends on the pelvic surface of the wing of the ilium. 



The tensor fasciae latse arises from the lateral border of the ilium and the 

 gluteus medius; it consists of two parts. The anterior part is long and rounded; 

 the posterior is shorter and fan-like. 



The gluteus superficialis is small. It arises from the gluteal fascia, the lateral 

 part of the sacrum, first coccygeal vertebra, and sacro-sciatic ligament. It is in- 

 serted below and behind the trochanter major of the femur, on the lateral branch of 

 the linea aspera. In some cases there is a bursa between the tendon and the tro- 

 chanter major. 



The gluteus medius has no lumbar portion. It is inserted into the trochanter 

 major by a strong tendon. There is a bursa under the tendon of insertion which 

 also extends under the gluteus profundus. 



The gluteus profundus is broad and fan-shaped. It arises on the superior 

 ischiatic spine and on the ilium as far forward as the gluteal line, and is inserted 

 into the trochanter major below the medius.^ 



The piriformis is not blended with the gluteus medius. It arises from the 

 border and ventral surface of the sacrum and from the sacro-sciatic ligament, and 

 ends on the trochanter major with or close to the gluteus medius. 



The obturators, gemellus, and quadratus femoris resemble in arrangement 

 those of the horse, and present no notable special features. There is a large bursa 

 under the tendon of the obturator internus. 



The biceps femoris has t^\'0 heads of origin which soon fuse. The larger head 

 arises from the sacro-sciatic ligament and tuber ischii, the smaller one from the tuber 

 ischii. The aponeurosis of insertion ends on the patella, the patellar ligament, 

 the fascia lata, and the tibial crest. There is also a tendinous band, which comes 

 from the deep face of the muscle and terminates at the tarsus, as in the horse. 

 There is usually a bursa between the muscle and the trochanter major. 



The abductor cruris posterior may be regarded as an accessory head of the 

 biceps femoris. It is a thin muscular band which arises from the sacro-sciatic 



1 Lesbre maintains that this is the scansorius, and that the gluteus profundus is so intimately 

 imited with the medius as to have been regarded by anatomists as part of the latter. 



