NEOPLASTIC DISEASES IN CHICKENS 19 



in the liv^er of the chicken and was a secondar\' finding in the livers of two cases 

 of myelocytoma. The livers affected with m\elocytoma were usually not so large 

 as those affected with lymphocytoma (Plate IV). The average weight of eight 

 affected livers was 5.65 percent of the body weight, with extremes of 14.6 and 

 3.2 percent (Table 11). The figure for average size is slightly high, for the value 

 in six of the eight cases was less than 5.65 percent. 



Table 11. — Summary of Data on Twenty Cases of Myelocytoma. 

 Figures in parentheses indicate number in group. 



Age at Necropsy Weight of Organs Expressed 



(Weeks) as Percent of Body Weight 



Died Killed Liver Spleen Kidney 



(8) (12) (8) (8) (4) 



Maximum 55 56 14.6 .86 .80 



Minimum 16 5 3.2 .37 .39 



Average 35.2 32.7 5.65 .55 .622 



Additional Notes: 2 cases were associated witli granuloblastic leukosis. 

 1 case was associated with embryonal nephroma. 

 1 case was associated with fowl paralysis. 



The spleen was involved in 12 of the 20 cases. The average size was 0.55 

 percent of the body weight in eight instances. Diffuse infiltration of the pulp 

 with neoplastic myelocytes was the characteristic finding. 



In eight instances the kidneys were affected. The degree of involvement varied 

 from a slight intertubular infiltration to almost complete replacement of paren- 

 chyma with solid masses of myeloc\tes. The average weight of four affected 

 kidneys was 0.622 percent of the body weight. This figure is not a fair example, 

 for it represents the findings on only two cases. 



Other organs and the number of times they were found affected are as follows: 

 gonad 13, parathyroid 8, thymus 6, lung 5, thyroid 5, adrenal 4, pancreas 3, and 

 heart 2. Histological examination was made of the lung and thymus in only 

 6 cases. The nerve ganglia of the anterior mesenteric plexus were infiltrated by 

 extension from the adrenal in 4 cases (Plate V, Figure 1). In 12 cases, there 

 were either sheetlike or nodular masses adjacent to the visceral or parietal peri- 

 toneum. A common finding was the arrangement of soft white nodular tumor 

 tissue near the ribs, concentrated at the costochondral junctions or on the sternum 

 (Plate IV). In one instance the tumor was spread along the spinal column of 

 the trunk, tending to infiltrate the bodies of the vertebrae, as in two cases de- 

 scribed by Mathews. The bones of the skull were affected with myelocytoma 

 in two instances (Plate V, Figures 3 and 4). In one, the process was confined to 

 the region of the nasal sinus; and in the other, the disease affected the dorsal aspect 

 of the cranium and was also found on the ventral aspect of vertebral column in 

 the region of the testis. 



A variable number of m,>eloc>'tes was noted in the lumens of the blood vessels 

 of tissues at the time of microscopic examination. Smears of the blood obtained 

 before death were available for study in only four cases. In several cases imprint 

 preparations of tumor nodules were prepared by staining with May-Grunwald 

 and Giemsa solutions for comparison with the myelocytes found in the blood 

 stream. The myelocytes comprising the tumor were found to be identical with 

 those in the blood stream and were at a nearly com.parable stage of development. 



