432 VEDDER AND CLARK. 



(slight indications of paralysis) , but became suddenly prostrated. 

 The vagus nerve showed almost no degeneration. 



Fowl 5 showed extreme peripheral neuritis, no prostration, 

 and little degeneration in vagus. 



Fowl 6 showed marked peripheral neuritis, no prostration, 

 and extensive degeneration in vagus. 



Fowl 8 showed marked peripheral neuritis, extreme prostra- 

 tion, and extensive and advanced degeneration in vagus. 



The vagus nerve of fowl 13 (Plate III, fig. 5) shows the extent 

 to which degeneration may progress in the vagus, and in our 

 series is relatively advanced degeneration for the vagus. In the 

 teased preparations of the vagus nerve of this fowl no single 

 nerve fiber could be found which did not show areas of blacken- 

 ing along its course. This was found to obtain in the vagus of 

 most of the cases; that is, that somewhere along its course in 

 segments of the nerve from 2 to 5 millimeters long, each fiber 

 showed one or more areas of blackening with the osmic acid 

 of Marchi solution. At the periphery of this illustration single 

 fibers may be seen showing frequent globules of fat along their 

 course. In those vagi showing little degeneration the blackened 

 areas are not so numerous. 



Plate III, fig. 6, is a high-power view of a teased preparation 

 of the same nerve. In this there will be seen rather large glob- 

 ules of degenerated myelin. This stage is about as far advanced 

 as has been observed by us. It will be noted that, while there is 

 a distinct globular arrangement of degenerated myelin, there is 

 no vacuolation of either degenerated myelin or of the medullary 

 sheath. In no case has there been observed a vacuolation of the 

 medullary sheath nor a collection of degenerated myelin into 

 very large globules as is found in the sciatic nerve or as is 

 very characteristic in peripheral nerves which show Wallerian 

 degeneration after section. There has not been observed a break- 

 ing up of the axis cylinder of the fibers of the vagus. These 

 observations lead us to believe that, although in polyneuritis in 

 fowls each nerve fiber of the vagus may, and usually does, show 

 degenerative changes by the Marchi method, this degeneration 

 never progresses far enough before the death of the fowl to bring 

 about the destruction of the axis cylinder. 



Cervical ganglion and its pre- and postganglionic fibers. — The 

 superior and inferior cervical ganglia from several cases were 

 examined by the Marchi method for degeneration. Very small 

 droplets of fat, approximately one-half micron in diameter, were 

 observed in many of the ganglia cells. However, these were by 

 no means numerous, ranging from 4 or 5 to 20 or 30 in a cell. 



