Excerpted from Dux Dubitantium 1.71

It follows from this that it attracts a humor which is warmer or colder than it should be, or thicker or thinner. And because of this the passages of the humors are blocked, and putrefaction occurs, and the quantities and qualities of the humors are turned into their opposites. And from this diseases arise, like scabies and pruritis, and great wounds. So it is in leprosy, and the ulcer eating away at the flesh until the form of the limb or limbs is destroyed. This is the argument in these four faculties, and according to the same means it happens to all beings, since it is this which generating things generate, and it brings the permanence of its being within a certain time. ... This same thing is the cause of renewal of the harmful things in the world such as storms and heavy rains, and snow, and hail, and whirlwinds, and thunder, and lightning, and pollution of the air.

original latin

Et dixerunt quod ista poena inflicta pro lingua mala quae in hoc. Et quod ista plaga incipit a domibus. Quam si convertit homo a peccato suo, et sanatur illa plaga. Si vero perseverat in stultitia sua, plaga adhaeret vestibus, postea vero corpori.

Utilitas autem huius credulitatis est manifesta. Praeterea alia est utilitas, quia lepra transit ad alium et homines abhorrent eam naturaliter. Rationem vero munditiae leprae qua debet fieri cum ligno cedrino, et origano, et cum tinctura rubea, et cum duabus volucribus, sapientes ostenderunt nobis et causam eius et non congruit illud rationi ligni cedrini, nec origani, nec coloris rubei quantum ad vitulam rusam. Similiter non inveni rationem cui invitant in manipulo origani cum quo effundunt sanguis arietis paschalis.

Sic sunt causae generationis in hoc mundo generabili et corruptibili. Huius rei exemplum est. Istae quatuor virtutes quae inveniuntur in omni corpore nutribili, scilicet appetitiva, retentiva, digestiva, expulsiva. Si illae quidem essent sicut virtutes intelligibiles non operantes nisi quod esset conveniens et in hora competenti, et in mensura debita, evaderet homo multa genera nocumentorum et infirmitatum.

Huius rei explanatio est, quod si virtus attractiva non attraheret nisi utilia ex omni tempore. Et secundum quod necesse esset, evaderet homo infirmitates magnas et plagas. Sed quoniam istud non potest esse quia attrahit quamlibet humiditatem quae est attractabilis. Licet illa declinet in sua qualitate vel quantitate a linea rectitudinis.