A search of the morphological literature for comparisons with what a general histological survey has revealed in the liver of Terrapene carolina unearthed many unusual structures and arrangements: unusual in being other than what is seen in the mammalian species, such as rat and man, subject to most current hepatological study. What these structural specializations mean is unknown or speculative, but their significance may eventually prove to conflict with or modify some of the ideas derived from the well-spring of mammalian experimentation.
Given the immense number of vertebrate species and the diversity of hepatic microstructure among the relatively few examined, terms such as “typical” and “usual”, in logic, are unfounded. Nevertheless, some forms are met more often than others, and serve as the arbitrary point for designating departures. This contrivance may work for the mammals, but the piscine liver is very variable, and the few livers viewed in the other classes cannot indicate which, if any, scheme is predominant, and, moreover, reveal a notable intra-specific diversity.
The departures from the general state are set out in four tables, followed by comments. The variations are subdivided by vertebrate class, given no weighting, and are accepted as described by the various authors. (Table 5 presents proponents of a tubular architecture for the hepatocytic units of certain non-mammals.) The lists are neither exhaustive, nor always precise in attributing priority of observation, since the aim is to call attention to the extent and kind of microscopical variation in a format that can be readily scanned and amended.