No. 3.] PERIPHERAL NERVES. 725 



at right angles to it. Many of the bundles {c) are cut trans- 

 versely or very obliquely, and some are wavy or of a corkscrew- 

 shape. This is even more apparent in cross-sections of this 

 tissue. PI. XXXV, Fig. 21, represents a portion of such a 

 section. In this some of the bundles of nerve fibres {e) are 

 seen in longitudinal section. A comparison of this figure with 

 PI. XXXV, Figs. 17 and 18, which show portion of a cross- 

 section of an implanted nerve segment, and the bundles of new 

 nerve fibres which have grown through it, 152 days after its 

 implantation, is of interest. In PI. XXXV, Figs. 17 and 18, 

 the bundles of nerve fibres are separated by a relatively small 

 amount of fibrous tissue, and all the bundles are seen in cross- 

 section, which could only be the case, if they had a course 

 which was nearly straight, while in PI. XXXV, Fig, 21, the 

 fibrous tissue predominates, and the very tortuous course of the 

 small bundles is evident from the fact that they are met not 

 only in cross but also in oblique and longitudinal sections. 



In Exp. 40 no return of functional activity was obtained. 

 The central ulnar stump terminated in a large bulb, from 

 which bundles of young nerve fibres are given off. They 

 can be traced only for a short distance into the cicatricial 

 tissue below the bulb. In the connective tissue, just above 

 the central end of the peripheral stump, a remnant of the 

 implanted catgut bundle, about i>^ ctm. long, was found. In 

 cross-section, the eight threads implanted, are very clearly 

 visible. They appear somewhat broken up, and have been 

 permeated by polynuclear leucocytes and connective tissue 

 cells. Why only a portion of the implanted catgut bundle was 

 absorbed, and not all of it, I am not able to explain. It may 

 be that the unabsorbed threads proved an obstacle to the down- 

 growing axis cylinders which could not be overcome, and this 

 may have prevented their reaching the peripheral ulnar, a sup- 

 position, which, if correct, would go to show that the down- 

 growing axes reach the peripheral portion of the resected nerve 

 through the looser fibrous tissue supplanting the absorbed 

 catgut threads. 



