Fig. 3.

Photographs and reference tracings of cryosections of the sciatic nerve and surrounding tissue after injection of 0.5 ml black ink through a block needle that produced motor stimulation with a threshold of 0.3 mA in a hyperglycemic dog. A is the likely site of needle placement (arrow) because there is an accumulation of free ink and there is bleeding in and adjacent to the nerve. A somewhat more distal image (B) shows mores clearly that there are streaks of ink within the epineurium (heavy line) among the fascicles of the nerve (lighter lines). The ink distribution is represented in gray shading. The injection pattern was categorized as within the nerve.