TABLE 2.

Plaque sizes on MDBK cells

Virus	Size (mm)a	SD (mm)	% of wild type	Pb
PRV Be	0.78	0.11	100
PRV 91	0.55	0.06	70	<0.005
PRV 162	0.79	0.11	101	0.947
PRV 166	0.81	0.09	103	0.169

^aAn average of 48 plaques were measured 48 h after infection. 

^bP with respect to PRV Be was determined by Student's t test.