Diseases of the Circulatory System 185 



Thrombosis 



This disease is characterized by the clotting of the blood 

 in the great blood vessels and sometimes also in the heart. 

 Sometimes the corpuscles settle out of the serum so that a 

 part of the clot is clear. 



Diagnosis. — This condition is not capable of diagnosis 

 except at autopsy. Birds which show this condition, how- 

 ever, are often those which have been sick several weeks. 

 They are usually in poor flesh and a gradual loss of appetite 

 is often noted for some weeks before death occurs. 



Etiology. — The cause of this disease is unknown. 



Treatment. — As the disease is only recognized at autopsy 

 no treatment is possible. 



LeukoBmia 



Various cases of an alteration in the number of white 

 corpuscles in the blood of fowls have been described. Ac- 

 cording to Warthin ^ in normal hen's blood the proportion 

 of red blood corpuscles to white is 105-225 : 1, and only 14 

 per cent of the white cells are large lymphocytes, while in 

 leukaemia of fowls the proportion of red to white cells may 

 be less than 2 to 1 and a differential count of the white cells 

 shows that there may be 84.5 per cent large lymphocytes. 

 The tissue changes consist in tumorous nodules and infiltra- 

 tion of lymphoid cells in the liver, spleen, bone marrow and 

 other organs. 



From the literature it appears that investigators have 

 found several different blood diseases which show the blood 

 picture described above. Hirschfeld and Jacoby ^ and 



1 Warthin, A. S., " Leukemia of the Common Fowl." Jour. 

 Infect. Diseases, Vol. 4, No. 3, pp. 369-381, 1907. 



2 Hirschfeld, H., and Jacoby, M., Berlin. Klin. Wchnschr. 

 Bd. 46, pp. 159, 160, 1909. 



