CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE. 

 MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE. 

 E. L. MARK, Director. No. 20S. 



DEGENERATION IN THE GANGLION CELLS OF THE 

 CRAYFISH CAMBARUS BARTONII GIR. 



HANSFORD MacCURDY 



WITH NINE FIGURES 



INTRODUCTION 



Much of our knowledge of the changes occurring in the central 

 roots of nerves and their ganglia after the nerve trunks have been 

 severed has accumulated during the last two decades. In the 

 earlier observations and experiments, attention was directed 

 chiefly to the nerve roots and their related ganglia. From various 

 causes, including the complex character of the nerve centers, the 

 earlier investigations did not include the ganglion cells. Only 

 comparatively recently has attention been directed specially 

 to the ganglion cells and the changes occurring in them. 



It was suggested to me by Professor G. H. Parker that the large 

 nerve cells of the abdominal ganglia of the eastern crayfish, Cam- 

 barus bartonii, would afford favorable material for the study of 

 the changes in the ganglion cells after their nerve fibers had been 

 severed. Inasmuch as the investigations hitherto reported have 

 been on the nerve cells of vertebrates, the additional purpose of 

 extending our knowledge to an invertebrated animal would also 

 be served. 



As it is well known, Waller held that only those parts of the 

 nerve fibers degenerate which are separated from their nerve 

 centers. For many years this view prevailed. In time, however, 

 from observations made in cases where limbs had been amputated 

 which revealed an altered condition of the nerve roots and their 

 ganglia, doubts arose as to whether Waller was correct in limiting 

 the changes to the peripheral parts of the affected nerves. The 



