The Application of Walker's Index of Functional Normality to a Study of Developing Chick Embryos Infected with the Levaditi Strain of Vaccinia

Rachel E. Hoffstadt, Helen B. Tripi
1946 Journal of Bacteriology  
Two methods are generally employed for analyzing results obtained in studies of the growth of viruses on developing chick embryos: (1) counting of pocks and changes in the structure of the egg membranes and (2) estimation of the percentages of deaths among the embryos. No attempts have previously been made to record the changes of functional normality of the developing chick during the experiments. In most cases the morphology of embryos observed when the eggs were candled has been used to
more » ... s been used to determine the age and development of the embryos. This procedure has not always been reliable because the source of the eggs is often a commercial hatchery and the eggs are not from controlled flocks. Walker (1938) , in a study of normal stages of the development of chick embryos, suggested the use of the crown-rump length in conjunction with the wet weight, expressed as index values, as a criterion for determining variation in functional normality. He used the formula I = 1O000 to calculate these
doi:10.1128/jb.52.6.617-627.1946 fatcat:nmvdosqopzcm7dret7mwrleu2u