The morphological structures of the rickettsiae of epidemic and endemic typhus fever, Rocky Mountain spotted fever, and Q fever are similar to one another and to certain bacteria. The rickettsial organisms in common with the elementary bodies of vaccinia virus and all bacteria would appear to have a limiting membrane which surrounds a substance that seems to be protoplasmic in nature; numbers of dense granules are embedded in the inner protoplasm.
Endemic Typhus Fever