16 MASS. EXPERIMENT STATION BULLETIN 391 



comparable with more recent results obtained by experiments indicating a trans- 

 missible character for fowl paralysis and a possible etiological relation with lym- 

 phocytoma. Opposed to the results indicating experimental transmission of 

 fowl paralysis are experiments of other investigators who obtained negative 

 results. 



The present study, being confined to observations on pathological anatomy of 

 lymphocytoma, does not permit conclusions on questions concerning etiology. 

 Deductions, therefore, must be considered in this light without regard to the 

 results of transmission experiments. 



The pathology of the nerve lesions seen in fowl paralysis has been described 

 as both inflammatory and neoplastic in character. The inflammatory lesions 

 consist of an infiltration with polyblasts (lymphocytes, histiocytes, and plasma 

 cells), oftentimes associated with a proliferation of Schwann sheath cells and de- 

 generation of neurons in the ganglia. The infiltration may be mild and con- 

 fined to perivascular areas or diffuse; or dense and diffusely scattered in the nerves. 

 The inflammatory lesions are usually confined by the nerve sheath, although in 

 some instances a similar perineural infiltration may be observed. The neo- 

 plastic lesions difTer from the inflammatory in that the infiltrating lymphoid cells 

 have a neoplastic character, are actively multiplying, and m,ay be so aggressive 

 as to almost entirely replace the nerve elements within the nerve sheath. Such 

 neoplastic areas may readily encroach upon and penetrate the nerve sheath with 

 infiltration of the adjacent tissue. It would be a simple matter to separate cases 

 of fowl paraKsis into a group with inflammatory lesions and a group with neo- 

 plastic lesions if it were not for those cases in which one type of process seems to 

 merge into the other. Such a separation would, therefore, have to be made on a 

 purely arbitrary basis. 



The primary purpose was the study of a group of lymphocytomas and not of 

 fowl paralysis, which meant that it was necessary to establish certain criteria 

 for the cases to be included. Such a plan is based on the premise that lympho- 

 cytoma and fowl paralysis are different disease processes. In view of the tact 

 that lymphocytoma may be found in almost any tissue of the body, it did not 

 seem reasonable that nerve tissue would be immune or resistant to such a tumor. 

 The plan developed and followed for this study, therefore, was to include all 

 cases in which any organ or tissue, including nerve, was suspected of being in- 

 volved with neoplasia. Those cases of fowl paralysis in which gross examination 

 made it reasonably certain that the lesions were confined by the nerve sheath, 

 leaving the visceral organs free of neoplasia, were not included. The plan would 

 thereby exclude many cases of fowl paralysis in which the nerves were infiltrated 

 with neoplastic lymphoid cells, for these cannot be distinguished on gross exam- 

 ination from the cases in which the lesions are inflammatory in character (Plate 

 III, Figures 5 and 6). 



Among the 213 cases of lymphocytoma were 83 in which nerves were involved 

 (Table 2). Of this number (83), there were 23 cases in which the nerve lesion 

 or lesions were confined to an area in which the adjacent e.xtra-neural tissue was 

 likewise infiltrated with lymphocytoma. The question arises of whether or not 

 such cases represent an extension of the process from within the nerve to without 

 or the reverse. As judged from this material, it would seem that both would 

 occur. There were 19 cases in which nerve lesions were confined to either the 

 nerve of Remak* or the anterior mesenteric plexus and immediate nerve radical, 

 and lymphocytoma was found in the adjacent tissue of the gonad, peritoneum, 

 or adrenal. In the majority of these the pathology suggested that the tumor 



The main trunk nerve of the mesentery arising from both the anterior and posterior mesenteric 

 plexuses of the autonomic nervous system. 



