(HEF)) densely dispersed over the surface, and with others (i.e. hemagglutinin (HA)) spaced widely apart. The major glycoprotein (HA) is interposed irregularly by clusters of neuraminidase (NA), with a ratio of HA to NA of about 4-5 to 1. Lipoprotein membranes enclose the nucleo capsids ; nucleoproteins of different size classes