4 MASS. EXPERIMENT STATION BULLETIN 391 



were found in the group of cases studied. Other varieties found in the chicken 

 by others could be readily fitted into the general scheme as outlined. 



Table 1. — Schematic Classification of Neoplasms Found in Chickens, 



L Tumors of hemoblastic origin. 



A. Lymphocytoma 



B. Myelocytoma 



C. Leukosis 



II. Tumors of connective tissue 



A. Benign 



1. Fibroma 



2. Myxoma 



B. Malignant 



1. Fibrosarcoma 



2. Fibrochondrosarcoma 



3. Osteochondrosarcoma 



4. Histiocytic sarcoma 



C. Special forms of connective tissue tumors 



1. Neurogenic sarcoma 



in. Tumors of epithelial tissue (Epithelioblastoma) 



A. Benign 



1 . Papilloma 



2. Adenoma 



a. Hepatoma 



b. Cholangioma 



B. Malignant 



1. Adenocarcinoma 



2. Carcinoma 



C. Special forms of epithelial tumors 



L Th>'moma 



IV. Tumors forming blood and lymph spaces 



A. Hemangioma 



B. Lymphangioma 



V. Tumors of muscle tissue (Myoblastoma) 



A. Leiomyoma 



B. Rhabdomyoma 



VI. Tumors of serous membranes 



A. Mesothelioma 



VII. Tumors of pigmented tissue 



A. Melanoma 



VIII. Mixed Tumors 



A. Embryonal nephroma 



B. Carcinosarcoma 



C. Teratoma 



Despite the apparent simplicity of such a classification certain difficulties arise. 

 For example, thymoma has been placed under the general heading of "Tumors of 

 epithelial tissue" and might with equal justification be placed in the group of 

 connective tissue tumors or in the group of mixed tumors. In general the termi- 

 nology is that commonly accepted for the various types of neoplasia, although 



