182 Mammalia. 



sliglit incision should be made into the vein ; the pipe of the 

 injecting syringe inserted into the incision then made pointed 

 towards the body, and a hgature passed round the vein en- 

 closing the pipe. 



We may conveniently divide the course of the dissection 

 into two parts. 



I. Abdominal region. II. Thoracic region. 



The dissection of the Head will be more conveniently 

 treated of in a larger subject.* 



N.B. The student should have the skeleton of a Rat before him. 



The animal should be laid upon its back on a cork of suffi- 

 cient width to allow of the limbs being pinned out on either 

 side, by which means the body may be kept firmly in position. 



Eemoval of the Skin. To raise the skin from the ventral 

 aspect of the body one longitudinal cut should be made, 

 severing the skin only, in the middle line, the entire length of 

 the body, and the skin should be reflected to either side. 



Abdominal Muscles. After removing the skin, the first 

 muscle which presents itself, and which adheres very closely 

 to the skin, is peculiar to Quadrupeds, viz., the Panniculus 

 Carnosus, or Musculus Subcutaneus. This fleshy pannicle 

 is spread over the whole body ; the abdominal portion forms 

 a broad expansion, its fibres running from the shoulder to 

 the flank; on the supero-lateral area of the abdomen it is 

 thick and fleshy, especially behind the arm, below which it 

 sends a tendinous expansion which penetrates between the 

 caput muscles and the chest, and gets attached to the Pecto- 

 ralis Major and internal trochanter of the Humerus. It is 

 related externally with the skin ; internally with abdominal 

 tunic and muscles : its action is to corrugate the skin, bind 

 down other muscles, and assist in difficult expiration. 



This Panniculus should be removed, and there will then be 

 apparent a thin white median line, extending from the ster- 



* Tide Dissection IV., Sheep's Head. 



