The external ear is, of all organs, that most affected by degeneracy.[211] It is a cartilaginous organ extending from a bony base, without a bony framework for its support and with very deficient blood supply, on account of its distances from the great blood centres, so that any defect in the nerve centres which control the local blood supply is likely to affect its nutrition. As a cartilaginous organ it has no lymphatics, which of necessity affects its growth. The sensitiveness of the ear to vasomotor changes is evident by the results of the extremes in heat and cold, emotional blushing and fatigue. Galton reports a schoolmistress who judges the fatigue of her pupils by the condition of their ears. If the ears be white, flabby and pendant, she concludes that the children are much fatigued. If they be relaxed, but red, they are suffering, not from overwork, but from a struggle with the nervous system rarely under control in children. These states are very common among degenerates. To appreciate the degeneracy observed in the ear its embryology requires study. Before the end of the first month[212] there appears around the external opening of the first gill-cleft (Fig. 35) a series of six tubercles, two in front on the hind edge of the first visceral arch, one above the cleft and three behind it (Fig. 36). A little later a vertical furrow appears down the middle of the hyoid arch, in such a way as to mark off a little ridge which joins on to tubercle 3 and descends behind tubercles 4 and 5. The second stage is reached by the growth of all the parts; the fusion of tubercles 2 and 3 and the growth of the ridge down behind tubercle 5 to become continuous with 6. After these changes it is not difficult to identify the parts. [Illustration: FIG. 35.] [Illustration: FIG. 36.]