BuLb. U. S. B. P., 1925. (Doc. 972) 
9 
Fig. 5. — Microphototrapli of a Sfction through an older but as yet unbroken tumor. The epidermis is 
still continuous over the surface. The black area indicates the thickening of the dermis — 5 millimeters 
in thickness at the thickest portion shown. The portion marked X is shown enlarged in Figure 6. 
Fig. 6. — Microphotograph under higher power of the portion marked X in Figure 5. The extent of the 
dermis is evident, and comparison with the right end of Figure 5 will indicate the amount of thicken- 
ing above the normal. The extrusion of a lobe of the tumor into the epidermis is shown a little at the 
right of the center. The rounded black object in the epidermis at the left of the center is a section of 
another such lobe, and a third portion shows near the left border. 
Fig. 7 —Microphotograph of section of adipose fin, fully infected, but in an only slightly advanced 
condition. 
Fig. 8. — A similar section of an adipose fin at a more advanced stage of the disease. The connective tissue 
of the fin is entirely involved. The rounded cavities are large cystlike spaces filled with the bacteria, 
most of which were lost out in making the slide. 
Fig. 9. — A "young" tumor at the base of the caudal fin, experimentally produced by inoculation, as 
indicated in the text. Two months after inoculation. 
