DISSECTION OF THE DOG 



33 



costalis). If this be traced in a ventral direction, it will be found to reach 

 the middle line of the sternum, where it meets its fellow membrane of the 

 opposite side. From the sternum the two pleurae are reflected dorsalwards 



cava caudalis 



n. phrenicusWt- 



m. dbliquus 

 abdominis extemus 



m. rectus abdominis J 

 m. transversits thoracis 

 m. pectoralis profundus . 

 m. pectoralis super/icialis 



Fig. 10. — Transverse section of the thorax on a level with the eighth thoracic vertebra. 

 4, 5, 6, 7 = fourth, fifth, sixth, and seventh ribs. 



as th3 mediastinal pleura (pleura mediastinalis). Close to the sternum the 

 two pleurae are intimately associated and a thin double membrane is produced. 

 Soon, however, the heart intervenes between the two mediastinal pleurae 

 [here specifically known as the pericardiac pleura (pleura pericardiaca)], with 



D 



