Abstract
When avian infectious bronchitis virus (IBV) is fixed in formaldehyde, negative stain is able to penetrate the particle and an internal component is visualized. This component is seen as a tongue or flask shaped structure attached at one point to the outer virus membrane. A model yielding transmission patterns similar to the virus has been made. Gradient centrifugation studies on IBV reveal that the RNP is associated with the internal sac.