« logico-mathematical ». As will be seen, the most useful for the theoretical neuromorphology, along with geometry for metrical parameters, are the set theory, the system theory, the graph theory. Theoretical tools General morphology The classic traditional forms were emanating from and could be described by using Euclidean geometry for instance in relation to the cartesian triedre (one perpendicular axe for three "dimensions"). These forms can have material realisations (cubes, balls..). Many natural objects however cannot be satisfactorily described using the Euclidean geometry. Many of them are for instance fractals (Mandelbrot, 1983), because they are branched, have holes, or are too anfractuous, etc.. In their case the three dimensions are no more linked linearly. This is particularly true for surfaces and volumes. As already stressed by Stevens (1974) some morphological pattern may offer precise advantages. An example can be given from two extremes where the surface of objects is fundamental. The surface is the place where objects exchange between an inside and an outside. In the case where the more advantageous is to have the minimal exchange, the chosen shape is generally the ovoid (such are eggs, grains, fruits, cetaceans, etc. with the sphere as the perfect limit), which for a given volume limits the surface to its minimum. When the exchange is fundamental important surface is necessary an aminimal material cost. The binary branching increases considerably the surface without increasing much the volume of matter. This is the case for vegetal trees and vascular, pulmonary, urinary systems. The nervous system may be seen as a system of exchanges between emitting and receiving binary arborizations, offering a huge combinatorial range. Identification and classification One problem of neuromorphology is because it has not to describe one object, the brain, but an average brain. This justifies an extensive use of statistics. Tyner (1975) and Rowe and Stone (1977) have analysed the conceptual bases to be respected in the process of neuronal classification. They insisted on the necessity of separating classification and identification. Classifications must be based on multifactorial techniques and to be hierarchical (following the bicentennial animal taxonomy). When many namings or identifications were done on the characteristics of the soma, it appeared clear that only a quantitative study of complete dendritic arborisations was able to offer a means for a neutral neuronal taxonomy. A particular kind of a group of neuron in a localized part of the brain in one animal