[The application of quantitative methods in experimental morphology]

Quantitative analysis has assumed great importance for describing and appraising evolutionary and involutionary processes. Measurements alone do not permit conclusions regarding the laws governing natural development. The elaboration of biologically meaningful mathematical models is necessary for such purposes. This paper shows how functions with a terms can be used to describe skull and body growth under normal and experimental conditions (frontal biped model in Rattus norvegicus Berkenhout as a biological model). A model consisting of a 2nd order homogenous linear differential equation with constant coefficients has proved to be biologically meaningful for describing skull length and breadth, and for the gross body weight. In order to study different growth rates in control and experimental animals we have calculated "confidence intervals" for the graphs of the special solutions of the general integral. This permits optimum validity although no mathematically precise interpretation can be given.