IN the preceding pages it may have been observed that the adage, ‘There are no rules without exceptions,’ occurs so frequently in ophidian physiology that the latter are almost in the majority. Concerning the teeth especially, the forms of dentition in the various families, the distinction of species by them, the size and position of poison fangs, etc., the rules involve so many exceptions that we can perhaps render the subject less perplexing by dispensing with rules altogether. ‘The gradations of teeth are very imperceptible,’ said Prof. Huxley in his lecture at the London Institution. So numerous are their stages of development that there is really no well-defined gap between the venomous and the non-venomous species. ‘We do not know for certain whether the ordinary teeth are poisonous or not,’ Huxley also said. The recent researches into the nature of salivary secretions will throw more light on this subject. A large non-venomous snake, like other normally harmless animals, if biting angrily, with its abundant salivary glands pouring secretions into its mouth, might inflict a very ugly wound, especially on a feeble or frightened victim. A few rules may, however, safely be offered as ‘without exception,’ and these I will point out in order to clear the way a little towards a better comprehension of the exceptional ones. All true snakes, poisonous or not, that have teeth at all, have the six jaws described in the first chapter, viz. the right and left upper jaw, the right and left lower jaw, and the right and left palate jaw. The latter are called ‘jaws,’ not anatomically, but merely as answering the same purpose, being furnished with teeth; each true jaw and the palate being considered as two or a pair, on account of the independent action imparted to each by the especial muscles and the elastic tissue which unites them, where in the higher animals they are consolidated. With but one exception (the _egg-eating Oligodon_ or _Anodon_ family) all other true serpents, whether venomous or not, possess the two rows of palate teeth.