Japan was effectively isolated from the rest of the world from 1635 until 1854; there was no possibility of intromission of foreign genes to the cattle population during this time. Between 1868, the year of the Meiji Restoration, and 1887, some 2600 foreign cattle were imported. At first there was little interest in cross-breeding these with native stock, but from about 1900 it became widespread. It ceased abruptly in 1910, when it was realised that, while the cross-breeds might be larger and have better dairy qualities, their working capacity and meat quality was lower. From 1919, the various heterogeneous regional populations that resulted from this brief period of cross-breeding were registered and selected as "Improved Japanese Cattle". Four separate strains were characterised, based mainly on which type of foreign cattle had most influenced the hybrids, and were recognised as breeds in 1944. These were the four wagyū breeds, the Japanese Black, the Japanese Brown, the Japanese Polled and the Japanese Shorthorn.