6 S. B. VINCENT 



of the walls of one follicle muscle fibers run to the lower part of 

 another in the same series so that any movement is a general 

 movement. These may lay the hair back. They are all striped 

 fibers (fig. 5). 



Besides this connection of the follicles, there is a flat muscle 

 band of fibers which surrounds the follicle on three sides. It 

 originates in the wall of one follicle, runs around it and is inserted 

 at the same level in the walls of another follicle. This muscle 

 is well seen in a horizontal section (fig. 4). The nerve enters, as 

 Bonnet ('78) says, on the muscle free side. These muscles prob- 

 ably have to do with the constant quivering movement of the 

 hairs. 



About the neck of the follicle are both longitudinal and hori- 

 zontal contractile fibers and also about the neck running horizon- 

 tally are plain muscle fibers which lie just below the nerve ring. 



The conical body also has a muscular structure. The con- 

 traction of this organ opens the mouth of the follicle and permits 

 a free vibration of the hair for a considerable depth in the follicle 

 just as the contraction of the smooth fibers about the neck closes 

 the walls about the hair and dampens the vibrations. 



II. HISTORICAL 



Although the tactile hair has been the object of many and 

 extended studies, there are still histological and functional ques- 

 tions unsolved. The great size of its follicle tempts the unwary 

 investigator; those who study the skin upon which it is found 

 can not ignore it ; and to the complexity of its structure each new 

 histological method and stain must be applied. 



One is struck by the contradictory statements made in these 

 reports, particularly in the earlier ones; but the differences have 

 several explanations. These hairs have such a general similarity 

 to the body hairs and to the hairs of the head that the facts found 

 true of the one have been carried over, wrongly, to the other. 

 Then there is the false assumption that the tactile hairs of all 

 animals agree in structure. Dietl ('73) has shown, and his state- 

 ments have been confirmed by others, that there are two kinds 



