Examination of growth curves, which reflect changes in quantity of the products of viral multiplication over a period of time, offers a promising approach to further understanding of the phenomenon of viral reproduction. Henle et al. ' have described growth curves based upon the titers of pooled allantoic fluids from groups of eggs sacrificed at various intervals of time after inoculation of influenza virus. They have demonstrated the step-like nature of the rises in titer by means of "one-step " curves, which they obtained by utilizing the interfering action of non-infectious virus injected subsequent to the infectious inoculum. Blumenthal et al. ' have recently described a multiple-step growth curve based on the infectivity titers of a series of pooled fluids. Hoyle7 has studied curves based upon the titers not only of pooled fluids, but also of serial samples from individual eggs. Growth curves in individual eggs, which may be obtained relatively easily by the technique described by Green and Freymann, ' have an advantage in revealing significant characteristics which may be obscured when

Research on bacterial viruses has been stim-ulated in recent years by realization that their study may give some insight into the general problem of virus-host relationships. It is of in-terest to note that Henle and Henle (1947) have pointed out a number of striking similar-ities between certain bacterial viruses and those causing influenza. The analogies were most ap-parent in the phenomena of adsorption and of interference, as well as in effects on the metab-olism of the host. Subsequently, Henle et al. (1947) reported one step multiplication curves for the influenza virus, and more recently Briody and Stannard (1951) have indicated that vac-cinia virus increases similarly. The bacteriophage-bacterium relationship of-fers to investigators simple manipulative proce-dures for the study of host-virus systems, and advantage has been taken of this to the fullest extent in the investigations of the T system of Escherichia coli (Demerec and Fano (1945)). The seven viruses comprising this group have been examined biologically, physically, and chemi-cally; and most of our information concerning bacterial host-virus relationships has been de-rived from this research. Investigations concern-ing some members of the "T " phages were carried out as early as 1939 by Ellis and Del-bruick and have been conducted with increasing momentum since then. In view of the notable contributions which these studies have made, it seemed that investigation of another system might be rewarding, in part as a means of de-termining how uniform are viral characteristics and host-virus relationships. The host-virus system chosen for study is one which is rather far removed in the bacterial kingdom from the coli-dysentery group and con-1 This paper is based on this author's doctorate thesis deposited in the Yale University library.

Investigation of the early period of viral multiplication permits observation of certain discernible stages in the reproductive cycle. Detailed analysis of these steps ((a) combination of virus with susceptible cells, (b) synthesis of new viral particles, and (c) dissociation or release of virus) yields data concerning basic characteristics of the agent. This information is pertinent for purposes of classification, and to stimulate hypotheses concerning the nature of the reactions of a virus with susceptible host cells under conditions of natural infections. To obtain evidence concerning the characteristics of multiplication of the adenoviruses (1-3), investigation of 4 prototype viruses of this group was undertaken. A preliminary report of these studies has been made (4); detailed presentation of the experimental results forms the basis of this paper. These data indicate that the types 1 to 4 adenoviruses studied adsorb at a relatively slow rate to the host cells, strain HeLa cells; that the latent or eclipse period of the multiplication cycle is relatively long and is longer for types 1 and 2 than for types 3 and 4; that the incremental period of viral propagation is relatively