The Emotions. 785 



then, is another case of the overflow of stimulation of a certain class; that 

 is, coming from organs having certain connections to the periphery of 

 the body, and there ending in mechanical demonstrations in the unpurpo- 

 sive contraction of these unstriated muscles. Horripilation is common to 

 all the hairy mammals, to the birds, and to some reptiles. The erection of 

 the hair along the back, especially over the shoulders, and in some cases 

 over almost the whole body, and sometimes on the tail, has been ob- 

 served in monkeys, baboons, chimpanzees, gorillas, the hyena, cat, dog, 

 lion, bat and other carnivora, the peccary, hog, elk, goat and antelope, 

 horses and cattle, ant-eater, agouti and others. It is caused in these 

 animals by cold or by mingled rage and terror, or possibly by rage 

 alone. Abject fear has a contrary effect. The animal then shrinks 

 into himself as, much as possible, and tries to skulk away, but if it is a 

 case of desperation with retreat impracticable or unsafe, the hair rises. 

 In some, as in the dog, a simple resolution to fight appears sufficient, 

 and even when playing fight, dogs often get sufficiently in earnest to 

 raise their hair. With them it appears to have been so much the habit 

 that it has reached great facility. 



The panniculus carnosus, or sheet muscle, which covers the bod}' of 

 quiulrupeds directly under the skin, has been mentioned in chapter five. 

 It is a striated muscle, and is generally subject to the purposive will. 

 In many cases the arrectores pili are connected with the panniculus, so 

 that the latter assists in the process of raising the hair. In such cases 

 the raising of the hair may be, to a certain extent volunta^, but it 

 could not be completely so, as long as the immediate connections with 

 the individual hairs are made by unstriated muscles. In some cases 

 the large hairs, such as whiskers, called vibrissce are connected with 

 the panniculus by striated muscle fibres. In such cases the movements 

 of the separate hairs are subject to purposive control. The hedgehog 

 (erinaceus) has voluntary control of his spines, which are connected 

 with the panniculus, and erected by its contraction. The porcupine 

 ( hystrix ) also controls the erection of his long quils probably by the 

 same means. 



In the order of development the unstriated muscle comes first. This 

 is shown in the embryology of the higher animals, the voluntary 

 muscles being first formed unstriated, and afterwards becoming striped. 

 The larvae of some crustaceans have unstriped muscles which become 

 striated in the fully developed tinimal. The striped muscles must, 

 therefore, have become differentiated from the uustriped ; and it is 

 reasonable to conclude that where the muscles moving the hairs are un- 

 striped, their motion is due to emotional overflow, and, like blushing, 

 is uncontrolled by direct purpose. 



But it is possible to produce emotional demonstrations from siinu- 



