Laudator Temporis Acti

Erasmus, Adagia I vii 96 (tr. R.A.B. Mynors with his notes):

Mutuum muli scabunt
One mule scratches another

When rascals and men of no reputation admire and cry up one another. The image is taken from mules which, like other beasts of burden, have a habit of scratching one another with their teeth. The phrase is cited by Nonius Marcellus¹ as the title of one of Marcus Varro's Menippean Satires, and must surely be proverbial. Ausonius² in the second preface to his Monosyllaba: 'But to end with a proverb what I began with an adage, mules scratch one another.' Varro³ also mentions this in the third book of his On the Latin Language, though the wording is most foully corrupt, for which the passage of time is not so much to blame as the common run of printers, whose only object seems to be the utter extinction of all good books. For the text runs thus: 'Philoptorus, a female friend of the man who in old age calls a boy pusus and a girl pusa. The result will be mutuam mulinam.' I think we should read mutuum muli and understand scabunt. Symmachus⁴ in one of his letters: 'The proverb says that mules scratch one another, and for fear I may be within reach of that, I hold back behind clenched teeth what I would say in praise of you.' It looks however as if the adage could not be correctly understood except in a derogatory sense, as for instance if two ignorant men were to praise each other or two cripples or two rascals. This recalls Horace's⁵ anecdote of the two brothers who enjoyed mutual back-scratching and an exchange of panegyrics in turn.

Rome had two brothers; one the spoken word
And one the law pursued. And how they purred!
How oft reciprocal the butter flew! —
'Gracchus has met his match.' 'And Mucius too!'

He also criticizes poetasters who, bad as they are, listen to each others' recitations with rapture:

Alcaeus I in his opinion shine,
He soars a new Callimachus in mine.

96 Taken from Nonius; it looks like the second half of an iambic line, though Erasmus does not note this, as he usually does. Otto 1162; Tilley M 1396 One mule doth scrub another. The first of a small group of adages with related meanings.

1 Nonius Marcellus] p 115 and three other places; for the Menippean Satires see i vii 5n.

2 Ausonius] See i vi 64n; from the third preface of his Technopaegnion.

3 Varro] De lingua latina 7.28. The standard edition by G. Goetz and F. Schoell, Leipzig 1910, credits the recognition of the proverb in this corrupt passage to Pantagathus, who in 1508 was a boy of fourteen.

4 Symmachus] Epistulae 10.1.3; he was an orator of the fourth century AD. In his edition in the Monumenta Germaniae historica (Auct ant 6), Berlin 1883, O. Seeck says that the manuscripts read (a)emulos for mulos, and credits the correction to Maarten Lips, whose edition was published in Basel in 1549.

5 Horace] Epistles 2.2.87-9 and 99-100, the latter in the version of Sir Philip Francis (1756), which has already been used in i v 60. Horace, a devoted follower of the Lesbian lyric poet Alcaeus, means himself to be recognized as one of these characters; it is thought that the other, who likes to be regarded as a second Callimachus (the eminent Hellenistic poet), may be a dig at his contemporary Propertius.

See also I vii 97-99.

A. Otto, Die Sprichwörter und sprichwörtlichen Redensarten der Römer (Leipzig: B.G. Teubner, 1890), p. 232-233 (#1162):

Mútuum mulí scabunt***) lautete der Titel einer Satire Varros (p. 172 R.). Pompilius bei Varro l. lat. 7, 28 sic fiet mutua muli. Auson. id. 12 (27, 4 Sch.) ut, quod per adagionem coepimus, proverbio finiamus et mutuum muli scalpant. Symmach. ep. 1, 31, 1 videbor mutuum scabere. 10, 1, 3 hoc est, quod aiunt, mutuum scabere mulos, cui proverbio ne videar confinis u.s.w. Ennod. p. 20, 16 Vog. dum in praeconiis mutuum videmur scabere. Apost. 17, 20 τὸν ξύοντα ἀντιξύειν: ἐπὶ τῶν βλαπτόντων ἢ ὠφελούντων τινάς. ἀπὸ μεταφορᾶς τῶν ὄνων· ἀλλήλους γὰρ ἀντικνήθουσιν. Diogen. 8, 48 τὸν ξύοντα δ' ἀντιξύειν: ἐπὶ τῶν διὰ χάριν χάριτας ποιoύντων. 'Ein Esel kraut den anderen' (Düringsf. I n. 427), d.h. ein Beschränkter lobt den andern und streicht ihn heraus. *) — Vgl. Ter. Phorm. 267 tradunt operas mutuas (sie helfen und unterstützen sich gegenseitig). Diese letztere Redensart wird jedoch, wie mir scheint, mit Unrecht unter den sprichwörtlichen aufgeführt.

***) Es ist der Schluss eines jamb. Trim. oder troch. Tetram. S. L. Müller zu Non. p. 115, 19.

*) Nicht ganz zutreffend Riese a.a.O. ut facis mihi, ita facio tibi. Falsch Genthe, de prov. ad anim. nat. pertin. p. 7: In beneficiis referendis qui exspectat mutuam gratiam, pueriliter sentit.

A.E. Housman refers to the proverb ('mutua muli') in his interpretation of Martial 9.67, in his "Corrections and Explanations of Martial," Journal of Philology 30 (1907) 229-265 (at 248).

From Augusto Franzini:

An old professsor in my high school (1970...in Sardinia) used to say: "Asinus asinum fricat" in Latin, meaning that a donkey (i.e. a very poor student) is always going for the company, or contact, with another one.

Hat tip: Alan Crease.