Contamination is revealed where the contaminated witness on the one hand fails to show peculiar errors of its exemplar (having corrected them from another source), and on the other hand does exhibit peculiar errors of exemplars on which he does not in the main depend.
When a variant was noticed, it might be introduced into the new copy by correction, or it might be noted in the margin or between the lines, preceded by some such expressions as ἐν ἄλλῳ (κεῖται), ἐν ἄλλοις, ἤ, γρ. (= γράφεται), al. (=alibi or aliter), vel. When a copy furnished with this kind of primitive scribal apparatus served in turn as an exemplar to another scribe, he might do any of four things. He might preserve both the variant in the text (t) and the marginal variant (v) in their places; he might retain t and omit v; he might adopt v in place of t, without mention of t; or he might put v in the text and t in the margin. This confluence of readings from more than one exemplar is known as contamination.
The conception [of the historical-critical edition] excludes correcting an authorized witness document from another witness document. The result would be a contaminated text, or a version consisting of variants which though authorized, were authorized in different contexts, and which in the new context would form a new, unauthorized version that never existed historically and that the author never knew as a version. Such a ‘corrected’ version would be an unverifiable whole that even the editor as its producer could not vouch for either on the understanding of the whole as a concatenation of signs referring to one another, or in consideration of the notion that this structure changes with each variant.
Kontamination (lat. contaminare ‘durch Vermischung verderben’) Mischung verschiedener Textfassungen bei der Herstellung eines Edierten Textes (ursprünglich die Mischung unterschiedlicher Überlieferungsstränge).
Si parla di contaminazione quando nel corso della trasmissione di un testo sia avvenuto un contatto fra due o più testimoni diversi che abbia prodotto una copia contenente alcune lezioni dell’uno e alcune lezioni dell’altro testimone. Il termine ‘contaminazione’, di valore evidentemente negativo e mutato dal linguaggio specialistico della medicina, presuppone l’esistenza di un forma ‘pura’ (cioè non contaminata) di trasmissione, che procede soltanto in modo univoco e verticale: per ogni apografo deve esistere un solo antigrafo. Quando gli antigrafi che generano un apografo sono più di uno, ed esiste dunque una contaminazione, si parla di trasmissione orizzontale, perché nello stemma storico accanto a linee discendenti e divergenti verrano a trovarsi anche linee orizzontali e convergenti.
one speaks of “contamination” when a witness does not limit itself to reproducing (usually adding further innovations) the characteristics of a single antecedent (in Pasquali’s terminology: vertical tradition), but has significant errors in common with mss. from other families in the stemma (Pasquali, again, calls this horizontal or transversal tradition).
Alberto Varvaro (“Considerazioni sulla contaminatione…”, 191) rightly shifts the focus of the discussion to the causes of contamination, reviving the distinction between two types of perturbation in genealogical relationships: