	This much we may confidently affirm: that although both the Missal and the Breviary have been subjected from time to time to various modifications, often, as might be expected, in a Roman direction, the changes are singularly few and unimportant, and the Ambrosian Rite of today is substantially the same as that represented in the early Manuscripts. Indeed, since some of these documents come from places in the Alpine valleys, such as Biasca, Lodrino, Venegono and elsewhere, while the modern rite is that of the metropolitan cathedral and the churches of the city of Milan, some proportion of the differences may well turn out to be local rather than chronological developments. The arguments of the two principal theories are necessarily derived in a great measure from the internal evidence of the books themselves, and at present the end of the controversy is not in sight.