FLEXOK KEFLEXES 111 



psoas parvus, which should form the medial limit of the transection of the 

 ilio-psoas. 



Pectineus muscle and the superficial division of the obturator nerve 

 emerging from it may also be cut through — though this is not essential. 

 Close the wound. 



III. iii. (PI. IX, fig. 3.) Remove the clip-weight from left foot. On 

 the medial edge of the foot (left) feel for a bony tubercle half-way between the 

 point of the heel and the root of the first toe. This tubercle marks insertion of 

 tibialis anticus. Pinch up a fold of skin over this and snip off the skin-fold 

 with the strong scissors ; this avoids cutting the subcutaneous vein, which 

 a scalpel-cut always wounds. The tendon is displayed with a vein crossing it. 

 Tie a strong thread round the tibialis tendon near its insertion, and pass an 

 entomological pin through the tendon just distal to the ligature ; complete 

 the ligature-knot by tying it round the pin. Sever the tendon, well distal to 

 ligature, bypassing scalpel under tendon and shaving off a sliver of bone with 

 the tendon end ; free the detached tendon up for 3 cm. or so, liberating it 

 from annular ligament by incising latter. Sever extensor longus digitorum 

 close distal to annular ligament ; also the nerve, avoiding the blood-vessels. 



III. iv. Lay the preparation upon its right side. Expose left sciatic 

 nerve (PI. IX, figs. 1, 2). Make incision through skin, starting from a point 

 midway between tuber ischii and great trochanter and prolonged downwards 

 to close above and behind the outer condyle of femur. From the top end of 

 this incision carry a skin incision forwards for about 4 cm., and from bottom 

 end another for 2 cm. Reflect the skin-flap forward. At the level of the 

 tuber ischii a vein is seen coming up from postero-lateral aspect of thigh and 

 plunging between muscles. Carry incision into this intermuscular space and 

 follow the space downward. The gluteus maximus, in the cat a smallish 

 thin muscle, lies in front of this : cut its lower tendinous end and reflect it 

 upwards. Open the intermuscular space towards its depth : the sciatic trunk 

 will then be seen ; expose it carefully : the proximal part of the nerve-trunk 

 shows a large branch passing backwards ; this is the nerve to the hamstring 

 muscles ; cut it. Follow the nerve-trunk downwards ; it will be seen to 

 consist of two divisions, a smaller anterior between which and the rest of 

 the nerve-trunk runs the minute but obvious comes nervi ischiadici artery. 

 Enlarging the incision downwards, the two divisions of the trunk can be 

 followed to where they begin to diverge. Separate the posterior division, the 

 tibial (popliteal) nerve, from the anterior, the peroneal nerve, and pass 

 a thread round the tibial nerve at the peripheral end of the part in view. 

 Tie the thread tightly ; cut the nerve distal to the ligature and dissect it up for 

 about 4 cm. with fine scissors, using the ligature to lift the nerve as it becomes 



