Although genetics has led to new ways of thinking about many problems in dentistry, there are others for which the concept of a particulate gene has failed to provide a clearcut solution. Interest in dentistry is not only in those discrete differences that may be attributed to a single gene substitution but also in such compound characters as arch shape, tooth morphology, or facial bone relationships that differ among individuals. Study of the variation in such quantitative dental characters has been limited largely to twin studies' 2 and to the comparison of mean values among groups of individuals.3-6 In these studies several or many different measurements of dental characters were made and were treated as independent of each other, although it was generally recognized that such treatment disregards the correlations resulting from those common causative agents that affect the various examined characters. It is clear that such analyses cannot provide a true picture of the relationships among the different groups under study.During recent years the analysis of intercorrelated compound variables has attracted the attention of many statisticians. Powerful analytical methods have been devised for comparing and for testing the significance of differences between multivariate distributions and for examining and describing the interrelationships among the variables contributing to such distributions. Until recently, these methods have been used in anthropologic and biologic research by comparatively few workers. Both biologists and statisticians have, however, recognized the necessity of working together toward the construction of suitable models and for the solution of such complex problems. Both the need and the desirability of co-operative effort are evidenced by the current support of training in mathematical biology and by the many conferences on biology and mathematics that have been held during the past few years. This paper will discuss several multivariate methods that may be used in the analysis of dental data, illustrating the methodology with some data from families and from a dental growth study, and will outline some additional problems in dental research to which such statistical methods may be applicable.The observations of Wylie7 and Stein, Kelley, and Wood' suggest that, with respect to several cranio-facial dimensions, daughters and fathers are more alike than are daughters and mothers, and, conversely, sons appear to be more similar to their mothers. It is impossible to derive from these observations a hypothesis consistent with the theorems of

Sloan Foundation and the A. D. Williams Research Fund, Medical College of Virginia.

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ONE FIQWEHair color has long been considered a most useful criterion for distinguishing divisions of mankind and it has been recorded in many studies in physical anthropology. In most of these studies the colors have been determined subjectively, and have been assigned either names or grades determined by comparison of the hair with color charts, color wheels or standard colored hair samples. Although hair color is determined primarily by the amount and type of pigment present in the hair, there are many structural variables which enter into the production of the visible hair color. Among these are the medullation of the hair shaft, the distribution of cortical fusi and the type of cuticular scales found on the hair. Because of these variables, and because of the personal element involved in making subjective classifications of color, it has been difficult, if not impossible, for subsequent investigators to duplicate them. Many of the difficulties resulting from the use of subjective analyses of hair coloration have been discussed by Trotter ('39) in her review of hair color classification.Attempts to devise quantitative measures of human hair color have met with little success. Gardner and MacAdams

The case of a four year old white girl with a bleeding tendency characterized by the spontaneous occurrence of petechiae, ecchymoses and hemarthroses is presented. Laboratory studies indicate a deficiency of factor VII, with normal levels of all other clotting components, and a vascular deficiency possibly related to frequent upper respiratory infection. Serum from the patient and from four close relatives having reduced levels of factor VII is shown to correct the abnormal thromboplastin generation of Stuart factor-deficient serum. The rate of conversion of prothrombin into thrombin is markedly delayed in the patient’s plasma but essentially normal in that of other family members. The patient’s prothrombin conversion is corrected by the addition of normal or Stuart-deficient plasma. The partial thromboplastin time of the patient is somewhat prolonged. It is concluded that factor VII deficiency is inherited in this family as an incompletely recessive autosomal characteristic. The penetrance of the deficiency allele in the heterozygous individual appears to be variable. Analyses of the distributions of clotting factor levels in the family and in samples from the normal population indicate that an individual may vary greatly in his clotting factor levels, the average variation being nearly as great as the variation among individuals. The magnitude of the variation among siblings suggests that the penetrance of the factor VII deficiency allele is affected by extrinsic factors and that the observed population variation does not result from the occurrence of multiple alleles. It is suggested that sex may be a factor determining clotting factor levels. The bleeding of the patient is controlled by transfusion of plasma and by injection of a plasma preparation called ACC-76 (Behringwerke, Germany), the latter followed by a transient elevation of blood factor VII.

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