EN
Coronavirus 800 (18) propagated in the lung cells of the calf foetus (16) was purified and concentrated by: a) differential centrifugation, b) precipitation with PEG-6000, c) repeated haemadsorption-elution assay (9). The samples were examined under a transmissive microscope after prior negative staining. There were found many virions (Fig 1 and 2) with a typical morphology of coronavirus (2, 12, 13, 14, 15, 17). Besides, there were observed some particles with internal nucleoprotein in the form of a spisal or S-shape, and empty particles (Fig 5) with bilateral concave surfaces (fig 6). Unusual peplomers forming short (Fig 7, 8) and long filaments (Fig 9, 10) were also seen. However, to identify these unusual structures as corona- viruses or coronavirus substructures (Fig 11, 12) it is necessary to employ a specific method using labelled antibodies.