446 VEDDER AND CLARK. 



to find any demonstrable change from the normal. Much to 

 our surprise, however, nearly all the rods had disappeared 

 from practically every fiber of the sciatic shown in a longitudinal 

 section through the middle of the nerve. In the smallest fibers 

 a few rods were to be seen, but they were extremely scarce in 

 the large fibers. This condition obtained in the sciatic of both 

 fowls. The stainable material of the medullary sheath which 

 demonstrated itself in the form of rods in the normal fiber here 

 took on quite a different and surprising appearance. In the 

 7-day fowls it was seen as smaller, or larger, irregular, branched, 

 and anastomosing globules. A few fibers showed an apparent 

 swelling here and there and a more or less distinct network. 

 Plate VIII, fig. 15, is taken from the sciatic of fowl 24, and is 

 more or less typical for both birds. The globular arrangement 

 is well demonstrated — b is a fiber showing the swelling and 

 network arrangement. This was confirmed by the other methods. 

 This change in so short a time was so pronounced and remarkable 

 that with a little skepticism the normal nerves were again 

 worked over. These confirmed in every particular our first 

 preparations. With considerable enthusiasm, the remainder of 

 the series of fowls was examined, and a routine examination of 

 all the previous fowls was begun. The results were well worth 

 the trouble, for in none of these preparations was it possible to 

 find a single fiber which even approached in appearance that 

 of the normal fiber. It was the rarest instance that a single 

 rod could be found. 



Changes in the fibers from the remainder of the series (that is, 

 fowls fed for more than seven days on polished rice) were not so 

 pronounced over the 7-day preparations as this was over the nor- 

 mal. In fact the 11-day preparation resembles very closely the 

 7-day, and it is practically impossible to distinguish the 11- or 14- 

 day from an 18-day preparation. Later changes are shown in 

 Plate VIII, fig. 16, and Plate IX, fig. 17. In these latter subjects, 

 most of the fibers show little advance over the 7-day or over the 

 next preceding stage. There is, however, to be observed a general 

 tendency toward segmentation of the myelin in the 11-day, 14-day, 

 et seq. A few fibers here and there, on the other hand, show 

 progressive change. The stainable substance collects in larger 

 irregular globules and skeins, the remainder of the medullary 

 sheath being remarkably clear. (Plate VIII, fig. 16, fibers a, h, 

 c. d.) In fowls which have been fed for a longer period, a few 

 fibers show a still more pronounced collection of the stainable 

 material into large irregular masses and segments. Plate IX, 

 fig. 17 h, is characteristic of such a fiber. The other and great 



