Bethune (early thirteenth century), also grammars in rhyme, were widely
used. Logical treatises often mentioned in university programs of study
were _De Sex Principiis_ (On the Six Principles), written about 1150 by
Gilbert de la Porrée, a teacher of John of Salisbury; and the _Summulae_
of Petrus Hispanus (thirteenth century). In the thirteenth century
Albertus Magnus made a digest of all the works of Aristotle, which
proved to be easier for students than the originals, and which were
sometimes used in place of them. Among mathematical works of this
century were the _Algorismus_ (Arithmetic) and the _Libellus de Sphaera_
(On the Sphere) by John Holywood (Sacrobosco); and the _Perspectiva
Communis_, i.e. Optics, by John (Peckham) of Pisa. A treatise on Music
by John de Muris of Paris was produced in the early part of the
fourteenth century. All of these were well-known university text-books.
They appear in the list at Leipzig throughout the fifteenth century (see
p. 139).


4. UNIVERSITY PRIVILEGES

The privileges granted by civil and ecclesiastical powers constitute a
fourth important influence upon the growth of universities. Beginning
with the year 1158 a long series of immunities, liberties, and
exemptions was bestowed by State and Church upon masters and students as
a class, and upon universities as corporations. Masters and scholars
were, for example, often taken under the special protection of the
sovereign of the country in which they were studying; they were exempted
from taxation, and from military service; most important of all, they
were placed under the jurisdiction of special courts, in which alone
they could be tried. Universities as corporations were given, among
other privileges, the right to confer upon their graduates the license