Explanation of Plate XII (figs. 1-11):

'The figures with one exception were drawn under a zeiss D and ocular 4. The outlines were filled in with the Camera Lucida and an attempt made to colour the drawings like the particular specimen under examination.

Fig. 1. To show the first segmentation of the myeline in degeneration. Each segment completely enclosed in myeline, with a central piece of the axis cylinder. Experiment XX. 2 days. R. S. middle of forearm. Osmic acid and haematoxylin.

Fig. 2. To show the secondary fragmentation of the myeline (extreme case). Exp. XX. 2 days. L S. middle of forearm. Osmic acid and haematoxylin.

Fig. 3. To show the remnants of the disintegrating axis in the segments of myeline. Exp. XIII. 4 days. R. S. 3 in. below wound. Gold and haematoxylin. Nucleus stained blue in haematoxylin.

Fig. 4. The same. Exp. IIl. 7 days. R. S. Below wound 2 in. Picric acid and fuchsin stain.

Fig. 5. The same. Exp. III. 7 days. R. S. Below wound 2 in. Picric acid and fuchsin stain.

Fig. 6. To show the more rapid fragmentation of the myeline in the neighbourhood of the nuclei. Exp. III. 7 days. Gold and haematoxylin. Nucleus stained blue.

Fig. 7. To show the multiplication and migration of the nuclei of the sheath and greater absorption near nuclei. Exp. III. 7 days. Gold anld haematoxylin.

Fig. 8. The same. Exp. III. 7 days. Gold and haematoxylin. Fig. 9. An instance of apparent indirect division of nucleus. The progressing fragmentation of myeline. Exp. III. 7 days. Gold and haematoxylin.

Fig. 10. (Drawn under obj. C. oc. 4). To show fragmentation of myeline especially at nuclei, and the material containing fragments of myeline which fills the fibre. Exp. III. 7 days. Gold and haematoxylin.

Fig. 11. To show progressive absorptionl of myeline; the proliferation of the nuclei; the position of the nuclei with reference to the balls of myeline; and the collapse of the empty sheath. Exp. XI. 9 days. R. S. middle of forearm. Gold and haematoxylin.' (402)

Fig. 1 in text:

'The segments first formed in degeneration, unlike the normal appearance of the segments of Lantermann seen in fibres after the action of osmic acid, have a complete envelope of the myeline, as shown in Fig. 1, and the small interspaces between them are filled with a colourless material. In each of these segments is a piece of the original axis cylinder, at this time apparently unchanged. Many of the older histologists have asserted that the axis remains unaffected during the degeneration. On the contrary, even at this early stage the breaking of the myeline into segments is accompanied by, or causes a simultaneous breaking of the axis.' (371)

Figs. 2-8 in text:

'Shortly after the first cylindrical segments of myeline and axis are formed an irreaular fragmentation occurs in these segments in most parts of the fibre. The segmetnts break up into smaller or larger irregular pieces or balls, an extreme case of which is shown in Fig. 2. Very frequently in these irregular masses of myeline remnants of the axis cylinder can be clearly distinguished in all stages of disintegration as shown in Figs. 3, 4, 5. It should be stated that some of the large segments frequently persist in different portions of a fibre long after tlle other segments have broken into small pieces and become partially absorbed,-the process is very irregular. It is at the time that this breaking up of the cylindrical segments into smaller fragments becomes apparent that the increase in the size of the nuclei of the sheath and the growth of the protoplasm surrounding these rnuclei become clearly marked. In fact this secondary fragmentation is always visible first in the neighbourhood of the nuclei as shown in Figs. 6, 7, 8. The large rounded nuclei lie in the middle of the fibre, and close to them are the small drops or balls of myeline. For this reason we believe that one cause of this secondary fragmentation is to be found in the absorption which takes place under the influence of the nucleus and its suirrounding protoplasm.' (372)

Fig. 6 in text:

'As evidence of the actual absorption which is beginning to take place one finds, at this time, say the seventh day, in the fibres stained with osmic acid or gold, some of the balls of myeline in the neighbourhood of the nuclei left colourless by the stain, see Fig. 6. In the later stages the same fact may frequently be noticed at different parts of the fibre and always most clearly near the nuclei. See Fig. 11.' (372-373)

Figs. 7-8 in text:

'An interesting fact in connection with the inultiplication of the nuclei is the way in which they migrate. In the beginning, of course, there is a single nucleus to each internode. At the time the secondary fragmentation of the myeline is fully under way one frequently finds a number of nuclei in the space which an internode would occupy. Sometimes they are in pairs as though from a recent division, but in other cases one or more large masses of myeline will be found between. See Figs. 7 and 8. This latter appearance has been used to support the theory that there are several nuclei present in the internode in a normal fibre, but that they are hidden by the myeline. Such a view as this it is not necessary to consider at present. The only explanation of the appearance described that seems reasonable is that after division the nuclei migrate or may migrate to some distance and start the process of absorption at a new place.' (373)

Fig. 9 in text:

'By the 7th day a very active proliferation of the nuclei of the sheath has begun. The increase in their number is very striking. Our methods of hardening were not such as to show the method of multiplication of the nuclei, though we often found nuclei showing a dumb-bell form, i.e., an elongated nucleus constricted in the middle as though multiplying by direct division. There can be little doubt that the division is indirect, as we sometimes found, even after hardening in Mueller's solution, nuclei like that pictured in Fig. 9 which evidently represents a badly preserved mitosis.' (

Figs. 10-11 in text:

'From the 7th day to the 14th day the process of absorption of the balls of myeline with their contained fragments of axis cylinder goes on actively, yet quite irregularly. Fig. 10 from a nerve after 7 days shows very well the breaking-up of the myeline and the formation in between, especially at the nuclei, of an apparently liquid substance in which are contained numerous fragments of the old myeline. As the absorption progresses and the fragments of myeline become smaller and less numerous the direct participation of the nuclei in the process becomes more evident. The nuclei are much more numerous and are found clustered in and about the remaining balls of myeline as shown in Figs. 11 and 12, representing a degeneration of 9 and 14 days respectively. One often sees bits of the myeline partially imbedded in a nucleus, and this appearance is found from this time on well into the later stages of regeneration, as long, in fact, as any of the myeline remiains unabsorbed. After 14 days absorption has gone so far that long stretches may be found, as shown in Figs. 12 and 13, in which only small fragments of myeline are present. At such places the fibre consists of a homogeneous, apparently liquid substance lying in the old sheath, and of many nuclei, often in pairs or groups, the latter giving indication of an active proliferation. Yet at this time, 14 days, and even later, one sees many fibres in which the absorption has lagged behind the condition of what may be considered a typical fibre of this period. In one and the same fibre places will be found in which absorption has made rapid progress in spots, all the myeline having disappeared, while in other spots the large cylindrical segments have suffered scarcely any change. Examples of this are pictured in Figs. 14 and 15. However irregularly the process may go on the final outcome is the complete absorption of the remnanits of the old myeline and axis; though as we have said before, balls of the myeline may be found in certain fibres long after this period, even at the time when fully formed new fibres have beeu produced. As the absorption proceeds the old sheath collapses more or less. It seems at first to contain a liquid material with some debris of the old myeline, but this too finally disappears and the beginning of the actual process of regeneration is inaugurated by the formation of new protoplasmic material around the numerous nuclei contained in the fibres.' (373-374)