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 ree- 
tus. 
The rectus abdominis is attached by a long tendon on the first five or six costal 
cartilages, and by fleshy 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 em.) 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 thoracie and 
first three or four lumbar vertebra, 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 vertebre. 
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 lumborum is well developed, and extends laterally beyond the 
edge of the ilio-psoas. It arises from the last three or four thoracic vertebree 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 fascia late 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 coecygeal vertebra, and sacro-sciatie 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 — 
ischiatie 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 two heads of origin which soon fuse. The larger head — 
arises from the sacro-sciatic ligament and tuber ischii, the smaller one from the tuber | 
ischi. 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-sciati¢) 
‘ Lesbre maintains that this is the scansorius, and that the gluteus profundus is so intimately 
united with the medius as to have been regarded by anatomists as part of the latter. 
1 
