266 SHOULDER-GIRDLE IN MONOTREMES, 



M. PANNICULUS CARNOSUS. 

 Echidna. 



On the integument covering the ventral aspect of the aVjdomen 

 being reflected, the panniculus comes into view. There is no 

 difficulty in the dissection for about 4 to 5 cm. on either side of 

 the median line, since the ventral aspect is devoid of spines ; but, 

 as we approach the lateral region, the integument is reflected with 

 difficulty, since the bases of the spines pierce through it and end 

 in the panniculus which sends bundles of fibres to each spine. 



Starting from the postero-vertebral region, the muscular sheet 

 runs forward and outwards, winding round the lateral aspect of 

 the body, while more anteriorly it extends over the scapula and 

 cervical regions and on to the forearm. 



Following the muscle i-ound the lateral aspect of the body, we 

 then find it running as a continuous sheet over the abdominal 

 muscles, the fibres taking an antero-posterior direction, with an 

 inclination towards the mid-ventral line. 



Arriving at about the region of the metasternum this single 

 layer now becomes cleft into a superficial and a deep stratum. 



The superjicial Stratum of the Panniculus. — For convenience of 

 description this may be subdivided into three parts (which can be 

 actually shown to exist by a careful dissection) : an internal, a 

 median, and an external division. 



The internal is represented by a small bundle of fibres, which 

 springs from the internal border of the general sheet of panni- 

 culus, and which runs forward and inwards to meet a similar 

 bundle from the opposite side in the mid-line, and together are 

 attached to an aponeurosis in the region of the posterior part of 

 the mesosternum. 



The middle division (Fig. 1, Pn. S. M.) is much better developed, 

 and is a broad band of muscle (connected with a similar band on 

 the opposite side of the mid-line by a well-marked aponeurosis) 

 which runs forward and inwards until it arrives in the region of 



