The purpose of studying repair of nerves in experimental animals, such as the rat, is to perform model experiments in which the phenomena inaccessible to large scale investigation in human subjects may be analyzed under controlled conditions. It is neither intended nor to be expected that the results obtained in such model experiments will become immediately applicable for clinical use. What is to be expected, however, is that the lessons learned from those experiments, when properly interpreted in terms of the conditions prevailing in the human body, may furnish directives for clinical research and possibly clinical practice. In a preceding article 1 a method of reuniting severed nerves by means of arterial cuffs was outlined, and the superior results of nerve regeneration following "sleeve splicing" were described. Since that publication, the method has proved its value on several hundred experimental animals, including rats, chickens, rabbits, cats and monkeys. We have