Gratitude is extended to Dr. 3ames Cook and Dr. Albert Strafuss for serving on my advisory committee and for their guidance through my program. Special thanks is offered to Dr. Stanley M. Dennis for making possible my graduate program. I also want to thank Dr. James Higgins for assistance in the statistical analysis of the data, Frank Leatherman for the histotechnic procedures, and Duane Kerr for the photographic material. My thanks to my parents for the education they gave me, and to my parents-in-law for they support and encouragement. Special thanks to my husband for his help, encouragement, and love.

Frozen tissues were studied microscopically to determine their value for diagnostic purposes. Sections were taken from lung, liver, kidney, small intestine, and brain of ten diseased dogs that died or were euthanatized. Some tissues were frozen, held for two or seven days, and then formalin-fixed. Tissues that were formalin-fixed immediately served as controls. Freezing changes such as transudate, cell shrinkage, fractures, hemolysis, and hematin formation were a nuisance, but usually did not prevent making a diagnosis. Viral inclusions, microfilaria, fibrosis, and intestinal bacteria remained distinct.