1. Chick embryo extract given intravenously did not favorably influence the course of experimental tuberculosis in rabbits, although it did cause lymphocytosis and lymphoid hyperplasia.
2. The tuberculous animals treated with chick embryo extract showed lower values for hemoglobin and red blood cells than tuberculous controls inoculated from the same suspension.
3. Under the conditions of these experiments an increase in the number of young, immature cells in the lymph nodes was accompanied by more extensive tuberculous lesions in the lymph nodes and especially in the germinal centers of the nodes. A possible analogy to lymphatic tuberculosis in children is suggested.
4. The observations of previous investigators on the progression and later regression of lesions in experimental tuberculosis have been confirmed. The distribution, character, and extent of lesions have been studied and are presented in tabular form.
5. The presence and significance of tuberculous thrombi in the lungs are discussed.