MUSCLES OF THE HEAD. 217 



separated by several small independent muscular fasciculi, which are carried 

 from one coccygeal vertebra to another. (Leyh designates these the inter- 

 transversales of the tail.) It inclines the tail to one side. 



2. IscMo-coccygeus. (Fig 131, 41.) 

 \Synonym. Compressor coccygis I'trcivall.') 



A small, thin, wide, and triangular muscle, situated against the lateral 

 wall of the pelvis, at the internal face of the sacro-ischiatic ligament. 



It is attached, by an aponeurosis, to that ligament and to the ischiatic 

 crest ; it is then directed upwards to be fixed, by its muscular fibres, to the 

 side of the last sacral vertebra and the first two coccygeal bones. 



It is related, outwardly, with the sacro-ischiatic ligament, and inwardly to 

 the lateral sacro-coccygeus and the rectum. 



It depresses the entire caudal appendage. 



REGION OF THE HEAD. 



The head comprises a large number of muscles, of which only those 

 covering the bones of the face, and those which move the lower jaw and os 

 hyoides, will be described. The others will be studied with the apparatus 

 to which they belong. 



A.. Facial Region. 



This region includes those muscles of the head which form a part of the 

 framework of the lips, cheeks, and nostrils: that is, all those which are 

 grouped around the face, properly called. Authors are far from being 

 unanimous with regard to the nomenclature and description of these muscles. 

 Girard recognised eleven, to which he gave the following names : labialis, 

 alveolo-labialis, zygomatico-labialis, lachry mo-lab ialis, supernaso-labialis, super- 

 maxillo-labialis, supermaxillo-nasalis magnus, supermaxillo-nasalis parvus, 

 transversalis nasi, maxillo-labialis, mento-labialis. To these eleven muscles, 

 three of which are single, two others are added ; these were described by 

 Bonrgelat as the middle (intermediate) anterior and middle (intermediate) pos- 

 terior muscles, which Girard wrongly considered as belonging to the labial. 



1. Labialis, or Orbicularis of the Lips. (Fig. 110, 27.) 

 (Synonym. Orbicularis oris Percivall.) 



Preparation. Remove with scissors the skin covering the two portions of this 

 muscle ; afterwards the buccal mucous membrane and subjacent glands within the lips, to 

 expose its internal face. 



The labialis, disposed as a sphincter around the anterior opening of the 

 mouth, is regarded as the intrinsic muscle of the lips, and is composed of 

 two portions or fasciculi, one for the upper, the other for the lower lip. 

 United to each other at the commissures of the mouth, and confounded with 

 the superficial layer of the alveolo-labialis, which they appear to continue, 

 these two muscular portions also receive a large portion of the fibres 

 belonging to the majority of the extrinsic muscles, such as the supermaxillo- 

 nasalis magnus and supernaso-labialis. 



The orbicularis is not attached to the neighbouring bone ; its component 

 fibres affecting a circular form, have, consequently, neither beginning nor 

 ending, except in being continuous with other fibres. 



The internal face of the superior fasciculus responds to a layer of Ralivary 



