Since 1954 when consistent work with measles virus became feasible, there have been several reviews: Blattner2; Black, Reissig, and Melnick3; McCarthy4; and Warren,5 and prior to 1954 there were reviews by Enders,6 Grist,7 and Babbot and Gordon.8 It is intended here to examine certain observations which have been made by various authors on the changes which measles virus may exhibit when grown in vitro, to try to fit these observations together where possible, and to speculate where our information is lacking. Most of the studies which had to be considered related to growth in primate cells.
In its natural or wild state, measles virus is a very stable agent with nothing to suggest the existence of variations in antigenicity or virulence. By contrast, in the laboratory studies there are, even from the one Edmonston strain, a considerable number of different virus lines grown