89 



On Striated Musculak Fibres in the Skin of the Human 

 Lip. By Dr. Woodham Webb, Lecturer on Histology 

 at the Grosveiior Place School of Medicine, London. 

 (Plate VII, fig. 16.) 



Kolliker, Eylandt, Henle, and Lister have accurately 

 enough described the unstriped muscular fibres connected with 

 the hair-sheaths and sebaceous glands in the scalp and other 

 parts of the skin. These are now well known by the signifi- 

 cant name of Arrectores pili, given to them by Eylandt. 

 Huxley has also figured branched muscular fibres of the 

 striated kind attached to the ^dbrissse of the rat. But no 

 notice has yet been published of a series of striped fibres and 

 bundles of fi])res existing in the human lip, and having there 

 corresponding relations and actions. Such, however, may be 

 found proceeding, in numerous small groups, from the orbicu- 

 laris oris, and passing outwards through the corium. These 

 minute bundles of muscular fibre are thrown oft" from the 

 outer layer of the orbicularis oris, and are to be traced in 

 compact masses to the base of the liair-sheaths and sebaceous 

 glands. At this point the fibres separate, spread themselves 

 over the surface of the gland, form more or less close attach- 

 ments to the membrane investing the glandular structure, 

 and appear to interlace with each other. Above the gland, 

 they are reduced to the condition of independent fibres, 

 diverge somewhat widely, so that those from adjoining glands 

 cross each other, and continuing outwards, gradually lose their 

 striated character ; becoming at the same time much smaller. 

 They vJtimately merge into the connective tissue which forms 

 the basement membrane of the papillae, in the same manner 

 as the muscular fibre of the tongue is described by Dr. 

 Hyde Salter to pass directly into the bundles of the sub- 

 mucous connective tissue. It has not been observed that 

 any of these ultimate fibres are branched; nor are there 

 any traces of the coexistence of non-striated muscular ap- 

 pendages. The points of attachment below, around, and 

 above the glands and hair-sheaths, sufiiciently explain the 

 action of these muscles ; the nature of the part in which they 

 are situated accounts for the deviation in the arrangement 

 of the respective structures from that prevailing elsewhere ; 

 and it may easily be miderstood how, though so smaU indi- 

 vidually, these muscles, by their conjoint action, assist in 

 determining the expression of the parts about the mouth. 



