BY W, J. McKAY. 953 



different degrees of obliquity as regards the mid-line. Thus there 

 is a median bundle occupying the mid-line whose fibres run antero- 

 posteriorly. This is the M, interscutalis proprius of Hoffmann. 

 On the other side of this are bundles whose fibres run from 

 without inwards and forwards. These are the Mm. scutales 

 raediales. Between these sets of muscles, and occupying a higher 

 level, we have bundles running from within outwards and for- 

 wards. These are the Mm. pyramidales. Running from the 

 mid-line outwards across the latter muscles, and consequently 

 occupying a higher place, we find bundles called Mm. interscutales 

 majores. It is with these latter bundles that the fibres of the 

 internal oblique muscle fuse. 



If we follow the rectus forward we have the deeper layer still 

 attached to the ventral scutes, while the superior layer is con- 

 verted into the hyoid group of muscles, with the exception of the 

 mylohyoid ; and we thus get portion of that stratum named by 

 Humphry the " deep brachio-cephalic." 



M. OBLIQUUS EXTERNUS. 



M. cutaneus externus, Hoffmann ; Dergrosse, dicssere oder Seiten- 

 hautmuskel, D'Alton; Aeusserer, schiefer Bauchmuskel, Heusinger. 



The external oblique muscle consists of two layers. The super- 

 ficial of these is continuous with the fascia covering the dorsal 

 muscles. As we shall see later on this fascia is gradually replaced 

 by the superficial layer as we go towards the anterior extremity of 

 the snake. The deep layer is made up of a number of bundles 

 which spring from the fascia representing the lateral septum, lying 

 between the sacro-lum balls and the leva tores costarum muscles. 

 The bundles run outwards and backwards over the pretrahentes 

 costarum superiores, and coalescing with the superficial layer, the 

 whole muscle is inserted on the lateral scutes, its fibres gradually 

 fusing with the lateral portion of the rectus. 



If we follow the external oblique layer forward, we find that the 

 superficial layer which we saw represented but slightly in the 

 posterior part of the body, now becomes conspicuous, since the 



