This appalling natural destruction is related to that which animals experience. Myriads of insects, birds, and beasts fall victims to climatic changes or disease, and the survivors always emerge from the experience with enfeebled health, and with diminished vitality and power of resistance. It is no doubt to avoid these consequences that in surroundings espe, . ally unfavourable to man-the Sahara Uesert-we 'find, according to Emile Gautier,2 that the healthy and vigorous population of the Tuaregs never increases, but remains at a fixed number. This people, which has reached limits of destitution beyond belief, and which lives in a "state of nature ", almost naked on the arid soil, hardly better equipped than the jackals, exists and keeps vigorous and strong only at the price of a self-imposed reduction of its numbers by the precautionary limitation of the birth-rate. "A cooking pot, a violin, and an irrigator in bone and leather of native manufacture" form the only furniture of their tents. At such a cost the Tuaregs prevent the necessary reduction from being brought about cruelly and brutally by punger or disease.