CHAP. IV. IN ANIMALS. 101 hairs, feathers, &c. By the contraction of these muscles the hairs can be instantly erected, as we see in a dog, being at the same time drawn a little out of their sockets; they are afterwards quickly depressed. The vast num- ber of these minute muscles over the whole body of a hairy quadruped is astonishing. The erection of the hair is, however, aided in some cases, as with that on the head of a man, by the striped and voluntary muscles of the underlying panniculus carnosus. It is by the action of these latter muscles, that the hedgehog erects its spines. It appears, also, from the researches of Leydig 1S and others, that striped fibres extend from the panniculus to some of the larger hairs, such as the vibriss& of cer- tain quadrupeds. The arrectores pili contract not only under the above emotions, but from the application of cold to the surface. I remember that my mules and dogs, brought from a lower and warmer country, after spend- ing a night on the bleak Cordillera, had the hair all over their bodies as erect as under the greatest terror. We see the same action in our own goose-skin during the chill before a fever-fit. Mr. Lister has also found,10 that tick- ling a neighbouring part of the skin causes the erection and protrusion of the hairs. From these facts it is manifest that the erection of the dermal appendages is a reflex action, independent of the will; and this action must be looked at, when, occurring under the influence of anger or fear, not as a power acquired for the sake of some advantage, but as an incidental result, at least to a large extent, of the sensorium being affected. The result, in as far as it is 18 4 Lehrbueh dor Histologie des Menschen,7 1857, s. 82. T owe to Prof. W. Turner's kindness an extract from this work. 10 * Quarterly Journal of Microscopical Science/ 1853, vol. i. p. 262.