Human Physiology

near the ends of the row. The rows were so placed on the surface of the body as to form bands transverse to the animal's chief axis. In any given band the rows constituting it alternate with those of the two adjacent bands. The rows of quills break the integument up into plate-like areas, which the author interprets, in accordance with the conclusions of Weber and of others, as the remains of scutes with which the ancestors of mammals are supposed to have been covered. Judging from the condition of the integument in the porcupine, these scutes were large and well developed dorsally and small and poorly formed ventrally. In the porcupine the woolly hair makes its appearance much later than the quills, and may be formed on the scute areas. Phylogenetically the quills represent the primitive hairs, and these are distributed in conformity to the primitive scute coverinos. The woolly hairs, on the other hand, are a much later acquisition, and are distributed without respect to the places once occupied by scutes. As the skin of the porcupine contains no sweat glands, the animal will probably be found to have a summer and a winter pelage as an adaptation to temperature changes.

靠近行列的末端。这些行列在身体表面的排列方式是形成与动物主轴横向的条带。在任何特定的条带中，构成它的行列与相邻的两条条带的行列交替排列。豪猪的刺将外皮分割成板状区域，作者根据韦伯和其他人的结论将其解释为哺乳动物祖先可能覆盖的骨板的残余。从豪猪外皮的状况判断，这些骨板在背部大且发育良好，在腹部小且发育不良。在豪猪身上，绒毛出现的时间比刺晚得多，并且可能在骨板区域形成。从系统发育上看，刺代表原始的毛发，它们的分布与原始的骨板覆盖物一致。另一方面，绒毛是后来才获得的，其分布与骨板曾经占据的位置无关。由于豪猪的皮肤不含汗腺，可能会发现这种动物有夏季和冬季的皮毛，以适应温度变化。