It was also the policy of the Muhammadans, whose system is based on slavery, not to push their religious zeal too far, for, if all the natives were converted, where could they procure a constant supply of slaves, those who accept the teachings of the Prophet being _ipso facto_ entitled to their freedom? Hence the pagan districts were, and still are, regarded as convenient preserves, happy hunting-grounds to be raided from time to time, but not utterly wasted; to be visited by organised razzias just often enough to keep up the supply in the home and foreign markets. This system, controlled by the local governments themselves, has long prevailed about the borderlands between Islam and heathendom, as we know from Barth, Nachtigal, and one or two other travellers, who have had reluctantly to accompany the periodical slave-hunting expeditions from Bornu and Baghirmi to the territories of the pagan Mosgu people with their numerous branches (_Margi, Mandara, Makari, Logon, Gamergu, Keribina_) and the other aborigines (_Bede, Ngisem, So, Kerrikerri, Babir_) on the northern slopes of the Congo-Chad water-parting. As usual on such occasions, there is a great waste of life, many perishing in defence of their homes or even through sheer wantonness, besides those carried away captives. "A large number of slaves had been caught this day," writes Barth, "and in the evening a great many more were brought in; altogether they were said to have taken one thousand, and there were certainly not less than five hundred. To our utmost horror, not less than 170 full-grown men were mercilessly slaughtered in cold blood, the greater part of them being allowed to bleed to death, a leg having been severed from the body[191]." There was probably just then a glut in the market.