92 



EXEECISE Xy 



of a line drawn across between the anterior edges of the right and left iliac 

 crests, or a little in front of that line. Passing the finger forward along mid- 

 dorsal line from the 7th spinous process, make out in succession the 6th, 5th, 

 4th, and 3rd spinous processes. Make a skin incision parallel with the mid- 

 dorsal line about half a cm. to left of that, and from a level close forward of 

 the 4th spinous process in front to a level 2 cm. behind the 7th spinous process 

 behind. At each end of this incision make a transverse skin incision about 

 6 cm. long and extending somewhat farther to left than to right of the 

 longitudinal incision. 



Reflect and retract the skin laterally to each side. The silvery lumbo- 



Text-fig. 35. Cutting-pliers for laminectomy, below : above, billed 

 forceps for holding and lifting the vertebral spinous process vs^ith left 

 hand while the pliers cut the lamina. 



dorsal fascia is exposed, joining laterally, to left, the ext. oblique muscle of the 

 abdominal wall. Make two incisions, one either side of and close to the spinous 

 processes of the 4th, 5th, 6th, and 7th vertebrae, each right through the depth 

 of the muscle down to the bone, keeping close to the spinous processes. Then 

 an incision through the fascia into the muscular mass covered by it along a 

 a line just lateral to the easily-felt left articular processes of the same vertebrae. 

 Between the incisions the muscular tissue is removed by rapid dissection, best 

 started from the median side and running laterally, cleaning the dorsal surfaces 

 of the vertebrae (PI. YII, fig. 2). With the oblique-jawed bone-cutting pliers 

 (text-fig. 35) cut off the articular processes as fully and deeply as possible : the 

 spinous processes are left. Then cut away the spinous process of the 1st sacral 

 vertebra. Then, standing to left side of the preparation, take with the left hand, 

 by means of the oblique-billed bone-forceps (the ' lifting forceps ' (text-fig. 35) ), 

 the spinous process of the 7th lumbar vertebrae and lift it somewhat ; with 



