Quantitative relation between the thickness of the contractile cell capsule and two markers of quality of peripheral nerve regeneration at 9 weeks (Soller et al 2012). (The data in figure 4 were obtained in the same study.) The rat sciatic nerve was transected and the stumps were inserted inside collagen tubes with closely matched but nonidentical structures differing in half-life for degradation. The stumps were originally separated by a gap length of 15 ± 1 mm. Data obtained on the regenerated nerve formed at the midpoint of original stump separation, 9 weeks post-injury. Left: the number of myelinated axons decreased sharply with increase in thickness of the contractile cell capsule (between broken lines) surrounding the rat sciatic nerve regenerating nerve. Scatter plot of myelinated fibers number (r = −0.601, N = 18, p = 0.0084) against capsule thickness. Right: an inverse relationship was observed between the thickness of the contractile cell capsule and the diameter of the regenerated rat sciatic nerve. Scatter plot of nerve tissue diameter (square root of total myelinated area, r = −0.669, N = 18, p = 0.0024) as a function of capsule thickness. The resulting linear regression y = 0.6022–0.0032x (R2 = 0.552) is superposed (Soller et al 2012).