DISSECTION OF THE DOG 



In its course the sciatic nerve lies in succession on the deep gluteal muscle, 

 the tend. hi of the internal obturator, the gemelli, the quadratus femoris, the 



adductor and (possibly) the Semimembranosus muscles. It is covered by the 



piriformis, middle gluteal and biceps ; and the abductor posterior crosses it 

 obliquely in the proximal third of the thigh. As it cur\es round the region 

 of the hip joint the nerve lits on the oral side of the caudal gluteal vessels. 



The I tranches of the Bciatic nerve are as follows : ( I) A branch arising before 

 the - iatic leaves the pelvis, and dividing into twigs lor the piriformis, internal 



Obturator, and gemelli muscles; (2) nerves to the biceps, semit endinosus. 



semimembranosus, and quadratus femoris muscles. These Leave the sciatic 



in the form of a large common trunk, springing from the parent nerve on a 

 level with the highest part of the trochanter major; (3) a small nerve to tin; 

 posterior abductor muscle of the leg; (4) lnh/al tniainmis nerve of I In l<j 

 (n. cutaneus sura' lateralis). The two last-named blanches leave the sciatic 

 about the same point, this varying from just beyond the trochanter major 

 to about the middle of the thigh. If the Bciatic nerve divides unusually early. 

 the nerves to the abductor and the cutaneous nerve are brandies of the common 

 peroneal nerve. The cutaneous nerve gains the leg by r unning between the 

 semimembranosus, semitendinosus, and abductor muscles medially and the 

 biceps muscle laterally. 



X. en i i.i - ( kamaus.- The cranial gluteal nerve is formed by branches 

 from the sixth and seventh lumbar nerves (possibly also from the firs! sacral). 

 It leaves the pelvis by the greater sciatic foramen, passes out between the 

 piriformis and deep gluteal muscles, runs between the deep and middle gluteals 

 supplying both, and ends in the tensor fascia? lata-, mainly in the longer, oral 

 part of this muscle. 



N. gluteus caudalis. — This rises from the seventh lumbar and the first 

 sacral nerves. It accompanies the sciatic nerve on the medial face of the 

 piriformis, where it divides into two branches to end in the superficial and 

 middle gluteal muscles. 



A.\. ci.n.Kv < kvnialis et CATJDAUS. — Both the cranial and the caudal 

 gluteal arteries are branches of the parietal ramus of the hypogastric artery. 

 Leaving the parent vessel opposite the oral border of the piriformis muscle, the 

 cranial gluteal artery accompanies the nerve of the same name into the gluteal 

 mass of muscles. Very much larger, and virtually the terminal branch of 

 the parietal ramus of the hypogastric, the caudal gluteal artery accompanies 

 the sciatic nerve to the region of the hip-joint, and ends in the biceps and 

 semitendinosus muscles. 



M. obturator ixternus.— The origin of the internal obturator muscle 

 is within the pelvis, and. consequently, cannot be examined as yet. Its inser- 

 tion into the trochanteric fossa of the femur, how ever, should now be determined. 



Dissection. — Reflect the deep gluteal muscle, and so expose the origin of the 

 rectus femoris and capsularis muscles. 



