90 



THE OSTEOLOGY AND MYOLOGY 



able, nor even practically convenient in many cases, a somewhat different, and perhaps more 

 natural, method of grouping the muscles is followed. It is essentially similar to that lately 

 proposed in my treatise on the Myology of the Ornithorhynchns (Proc. Essex Inst., vi, 

 Mar., 1871, p. 127), although lacking some of the details of the latter, Avhich I was led to 

 adopt after the manuscript of the present memoir had passed out of my hands. 



Muscles of the Head. 



The general muscular envelope of the head and neck may be most conveniently consid- 

 ered here, in connection with the muscles proper to the cranium. Other muscles attached 

 to the skull fall naturally into a different division. 



Panniculus carnosus. — The entire head and neck are enveloped in continuous layers of 

 muscular tissue, of somewhat complicated distribution. Although the platysma myoides, 

 occipito-frontalis, and some other muscles of anthropotomy, together with some that are not 

 recognized in man, are included in this general envelope, it may without violence be 

 described as a single muscle, under the above name, with the following structure and 

 disposition: — 



A plane of muscular fibres begins over the shoulder and breast, and along the median line 

 of the back of the neck, directl}' beneath, and intimately adherent by cellular tissue to, 

 the skin. These fibres are the most superficial of all ; and will be removed with the skin, 

 if due care be not taken. They proceed forward, those of the side of the neck inclining 

 toward the middle line of the throat, and there meeting those of the opposite side, sur- 

 round the ear and eye, running a little way upon the former, meet along the median line 

 of the top of the head, and finally end by insertion along the border of the orbicularis oris. 

 This plane is continuous over the whole of the surfaces just pointed out ; but its extreme 

 thinness, even in the most muscular subjects, its intimate adherence to the skin, and the 

 varying direction of its fibres in different places, render it diflicult to trace in its entirety. 



Beneath it lie two other planes of fibres, partially distinct, partially blended with each 

 other and with the foregoing. One of these begins over the upper part of the breast, and 

 runs straight up the median line of the neck, in apposition, or rather in direct coalescence 

 with, its fellow of the opposite side, the two together forming a thin band an inch or more 

 broad. At a point about opposite the angle of the jaws, the muscle widens by an outward 

 sweep of its fibres ; thence, nearly to the symphysis, the direction of the fibres is trans- 

 verse. They form a transverse plane, each joined to its fellow along a median longitudinal 

 raphe lying between the plane first described and the digastrici ; mounting upon the side 

 of the head, over the masseter, and becoming lost upon the temporal fascia. This appears 

 to be the true platysma. 



The third plane of fibres, although properly a cutaneous muscle, has a very distinct 

 origin, not from the skin. It arises from the ligamentum nuchae, from the occipital crest 

 to a point opposite the apex of the scapula, just external to the trapezius, which it overlies. 

 It forms in the neck a broad definite plane of fibres, at first proceeding directly transverse, 

 and afterward inclining obliquely forward, as it approaches the median line in front. It 

 loses itself, on the front of the neck, in the general envelope first described. At the back 

 of the head the anterior border of this muscle first sends a slip up the ear, as will be more 



