[27] Darwin gives another explanation of this phenomenon which seems to me less probable. He states that animals erect their dermal appendages that they may appear larger and more terrible to their enemies.
But how can it be explained that these smooth muscles should be originally dependent on the will? In order to avoid the doubly improbable supposition that these muscles should have become smooth and involuntary, although preserving the same functions, Darwin has recourse to another explanation. 'We may admit,’ he says, 'that originally the arrectores pili were slightly acted on in a direct manner, under the influence of rage and terror, by the disturbance of the nervous system.’ 'Animals have been repeatedly excited by rage and terror through many generations; and consequently the direct effects of the disturbed nervous system on the dermal appendages will almost certainly have been increased through habit and through the tendency of nerve-force to pass readily along accustomed channels.’ 'As soon as with animals the power of erection has thus been strengthened or increased, they must often have seen the hairs or feathers erected in rival and enraged males, and the bulk of their bodies thus increased. In this case it appears possible that they might have wished to make themselves appear larger and more terrible to their enemies ... such attitudes and utterances after a time becoming through habit instinctive.’
'It is even possible ... that the will is able to influence in an obscure manner the action of some unstriped or involuntary muscles, as in the period of the peristaltic movements of the intestines, and in the contraction of the bladder.’[28]
[28] Ch. Darwin: The Expression of the Emotions, p. 103.
[29] Preyer: Die Seele des Kindes. Jena, 1882.
[30] Brehm: Thierleben, vol. iii. 1883, p. 601.
[31] From [Greek: kataplêx], [Greek: êgos], frightened.
[32] W. Preyer: Die Kataplexie. Jena, 1878.
[33] Lauder Brunton: On the Pathology and Treatment of Shock and Syncope, p. 8.
[34] Baglivi: Praxis Medica, liber. i, cap. xiv. s. 5.