Dr. Kassai Tibor szerk.: Parasitologia Hungarica 1. (Budapest, 1968)
necropsy material from one place showed,in every case ,distinctive lesions of both caeca and liver, with typical concentric hepatic foci, whereas in material from the other farm characteristic caecal lesions, enlargement of the liver with indistinct discolorations, but no focal lesions were found. Several transitional forms were found to exist between hepatic changes that macroscopically were scarcely discernible and the focal lesions considered pathognomic of blackhead. Enlargement of the liver was a typical finding in turkeys that died or were killed at the height of infection. In survivors regression of the liver to normal size took place over several weeks. On the enlarged liver the least conspicuous lesions were poorly demarcated discolorations of varying size, paler in colour than normal liver tissue, and seen only at high illumination (in sunshine) after the liver surface had been smoothed. In other - supposedly more chronic - cases the considerably enlarged liver showed round foci of coin size slightly depressed beneath the surface of the organ, yellowish or greenish in colour and of concentric pattern (Eig. l). In some cases these foci penetrated deeply into the parenchyma. Such lesions are not readily confused with those due to other diseases. The third type of lesion was encountered in the livers of turkeys that had recovered from blackhead, the concentric foci described above having been replaced by cicatricial tissue. Regeneration of the necrotic areas by cicatrization produced sharply contoiired discoloured spots on the surface of the liver. The cicatricial tissue was paler than the surrounding hepatic tissue,yet the more advanced the process of regeneration the less marked was the difference. Since, however, regeneration of liver cells was incomplete, .the larger areas of scar tissue imparted a spotted appearance to the liver throughout the lifetime of the bird, 2.) Microscopic lesions. Histological examinations were performed on a total of 50 turkey livers, partly to
