4 MASS. EXPERIMENT STATION BULLETIN 370 



(146). The more commonly observed form of erythroblastic leukosis is evidenced 

 by the presence in the blood of many immature erythroblastic cells and by certain 

 characteristic alterations of the tissues which have been discussed in a previous 

 report (155). The other form, anemic erythroleukosis, is recognized as a sub- 

 variety in which there are relatively few immature cells in the circulating blood. 

 The predominating feature is a marked anemia with only minor changes in the 

 tissues other than the bone marrow. Intermediary and transitional forms of 

 erythroblastic leukosis (between the anemic and well-developed forms) have also 

 been observed (155). 



Granuloblastic Leukosis 



Synonyms for this form of leukosis are: myeloid or myeloic leukosis (EUermann 

 42), myelosis myeloidea (Battaglia and Leinati 6), leukomyelosis (Kitt 121), 

 leucocytheniia (Bayon 8), and leukemic myeloblastosis (Nyfeldt 142). 



EUermann (38) described leukemic and aleukemic types of myeloid leukosis. 

 The leukemic forms were further subdivided into a myeloblastic and a myelocytic 

 form, but no sharply defined distinctions between the two were observed. The 

 disease described b>' EUermann as "aleukemic myelosis" has been regarded by 

 Mathews (137), Feldman (62), and Feldman and Olson (63) as a definite neo- 

 plastic process composed of myelocytes and designated as myelocytoma. Eller- 

 mann's "leukemic myelosis" has been recognized as being associated with and 

 caused by the exciting agent of fowl leukosis. It is differentiated from erythro- 

 blastic leukosis by the fact that the predominating immature cells in the circulat- 

 ing blood are of the granulocytic series. There are instances recognized in which 

 the blood reveals many immature cells of both erythrocytic and granulocytic 

 lines of development. In these last named cases the term "mixed leukosis" is 

 sometimes applied (Furth 71). 



TYPES OF DISEASE SOMETIMES CLASSIFIED AS "FOWL LEUKOSES" 

 Lymphocytoma 



Synonyms for this disease are: lymphatische leukose (EUermann 43), myelosis 

 haemocytoblastica (Battaglia and Leinati 6), aleukemic lymphadenoma (Butter- 

 field 22), lymphadenoma (Mathews and Walkey 138), lymphomyelose (Kitt 

 121), lymphomatosis, visceral-lymphomatosis and hemocytoblastosis (Johnson 

 107, 108), leucose a leucoblastes (Andersen and Bang 2), lymphosarcoma, and 

 lymphocytomatosis. 



Lymphatic leukosis was the third general type of leukosis considered by EUer- 

 mann (43) to be caused by the filtrable agent of transmissible fowl leukosis. It 

 is noteworthy, in the light of more recent work, that many of the cases described 

 by EUermann were of spontaneous occurrence in chickens that had not been 

 inoculated. 



This form of disease is described and given the name lymphocytoma by Feld- 

 man (62). Lymphocytoma may be regarded as a malignant neoplastic disease, 

 the undifferentiated lymphocyte being the type cell of the tumor. Andersen and 

 Bang (2) give an excellent description of the disease and suggest that the type 

 cell is the leukoblast. This designation would imply the potentiality of the type 

 cell to develop into either the granulocytic or monocytic series of blood cells 

 as well as the lymphatic series. As no such differentiation of the tumor cell 

 takes place it is better to regard the type cell as either a dedifferentiated or 

 undifferentiated lymphocyte. The liver is often the site of many large foci of 



