Abstract
Cartwright & Brown (1972) confirmed recently that only the Cocal and Argentina strains showed significant cross-reactions in complement fixation and serum neutralization tests. However, the infective skeleton-like particles produced by treatment with Tween-ether or Nonidet and the infective ribonucleoprotein (RNP) released by sodium deoxycholate showed considerable cross-reactions in both tests. On this basis the major cross-reactivity was considered to be associated with the RNP.