Guidelines for the development of comparative pathology.

Abstract

The purpose of comparative pathology is to develop a fuller understanding of pathologic processes in individuals of various species. Historically, we distinguish between direct and indirect findings. Direct sources are paleopathologic fossils. Indirect findings are historic and/or religious descriptions of epidemics. The philosophy behind the comparative approach depends primarily on the individuals of the species as units. The individual represents a concrete reality, whereas the other taxonomic categories are only theoretical entities contrived by human thought. Intraspecies-specific comparison and the interspecies-specific comparison are distinguishable. In intraspecies-specific comparison different individuals (races, breeds) of one species are compared, whereas in the interspecies-specific comparison individuals of several species are compared. Evolution and the comparative ontogenetic development of recent organisms explains how the variability of species came into existence. Consistency in evolution and uniformity is given by the fact that members of all phyla are still represented by some remaining species. Heterogeneity of organismic structures are more numerous but secondary. With the exception of the virus, the cell is remaining the unit of living matter, but viruses depend on cells for their existence. The majority of species, the eumetazoans and vascular plants, are built of true tissues developed by cell division, whereas higher fungi and some algae exhibit plectenchymata which develop by the fusion of cells. This short article presents some thoughts and principles underlining the importance of development of guideline for the study of comparative pathology.