[30] “Pestilentis morbi gravissimum symptoma est, quod zonam vulgo nuncupant. Ea sic fit: Pustulæ nonnunquam per febres pestilentes fuscæ, nigræ, lividæ existunt, in partibus corporis a glandularum emissariis sejunctis, ut in femore, tibia, capite, brachio, humeris, quarum fervore et caliditate succi corporis attracti, glandulas in trajectione replent, et attollunt, unde bubones fiunt atque carbunculi. _Ab iis tanquam solidus quidam nervus in partem vicinam distentam ac veluti convulsione rigentem producitur, puta Brachium vel tibiam, nunc rubens, nunc fuscus, nunc obscurior, nunc virens, nunc Iridis colore, duos vel quatuor digitos latus._ Hujus summo, qua desinit in emissarium, plerumque tuberculum pestilens visitur, altero vero extremo, qua in propinquum membrum porrigitur, carbunculus. Hoc scilicet malum vulgus zonam cinctumve nominat, periculosum minus, cum hic tuberculo, illic carbunculo terminatur, quam si tuberculum in capite solum emineat.” p. 198. CHAPTER III. CAUSES.--SPREAD. An enquiry into the causes of the Black Death, will not be without important results in the study of the plagues which have visited the world, although it cannot advance beyond generalisation without entering upon a field hitherto uncultivated, and, to this hour, entirely unknown. Mighty revolutions in the organism of the earth, of which we have credible information, had preceded it. From China to the Atlantic, the foundations of the earth were shaken,--throughout Asia and Europe the atmosphere was in commotion, and endangered, by its baneful influence, both vegetable and animal life.