Abstract
The surfaces of Pasteurella haemolytica, biotype A, serotypes 1, 2, 6, 7 and 9 and of P. haemolytica, biotype T serotypes 3, 4, 10 and 15 were examined by transmission electronmicroscopy with ruthenium red staining and polycationic ferritin labelling, by scanning electronmicroscopy, and by light microscopy. Electronmicroscopy showed that the surface of strains of P. haemolytica biotype A was covered by irregular protrusions which were probably capsular material. The surface and general morphology of P. haemolytica biotype T were distinct from those of biotype A.