STUDY OF POLYNEURITIS GALLINARUM. 433 



but not in more than one-third of the cells. In the medullated 

 pre- and postganglionic fibers larger, though fewer, globufes of 

 fat were seen. It was found very difficult to tease the ganglia, 

 and sections after paraffine embedding were made. It is thus 

 quite possible that the degeneration here observed does not 

 represent the full extent to which degeneration had progressed 

 in these fibers. In the nonmedullated fibers no multiplication of 

 the nuclei of the neurilemma was observed. Thus, while there 

 are indications of degeneration in the sympathetic ganglia (that 

 is, cervical ganglia) and their fibers, this degeneration is slight, 

 and a careful search must be made to detect it. 



The sciatic and its pcripJieral branches. — Most of the investi- 

 gators who have undertaken a study of polyneuritis in fowls 

 have taken the sciatic as a basis for their anatomical study, and 

 have confined themselves to the Marchi stain. In most cases all 

 that was desired was to know if degeneration had or had not 

 taken place. Thus far the Marchi method is an excellent one 

 and well adapted for the purpose. On the other hand, to obtain 

 an opinion as to the extent of degeneration, an indication of the 

 probable changes which have occurred within the nerve, including 

 the condition of the axis cylinder and nuclei of the neurilemma 

 sheath, the Marchi method must be supplemented by other 

 staining methods. In our study of the degenerative changes oc- 

 curring in the sciatic nerve we have employed the Marchi; the 

 Weigert stain for myelin sheath; the Altmann, the Benda, and 

 the Meves mitochondria methods; the Golgi, Cajal, Mallory, 

 f uchsin, and saf ranin methods for the axis cylinder ; and haema- 

 toxylin methods for the nuclei of the neurilemma sheath. 



As in the case of the vagus, in those sciatic nerves in which 

 degenerative changes are apparent by the Marchi method, prac- 

 tically every fiber shows some indication of degeneration within 

 short limits of its course (2 to 5 millimeters) . The degenerative 

 appearances, however, vary within the widest limits in the 

 various fibers of the same nerve. In nerves from well-marked 

 cases many fibers show only slight changes — small black droplets 

 or a localized slight blackening — here and there at relatively wide 

 intervals, from 100 to 500 microns along their course. Other 

 fibers, and these form the majority of the fibers, show more 

 extensive change — larger and more frequent droplets of degen- 

 erated myelin. A certain proportion of the fibers from well- 

 marked cases of neuritis show advanced degenerative changes. 

 These make up from 10 to 15 per cent of the fibers. Whether 

 the other fibers show advanced degeneration at other places we 

 could not prove beyond doubt, but regeneration experiments, 



