MANUAL 



OF 



PRACTICAL ANATOMY. 



THORAX. 



T^HE dissection of the thorax is commenced on the thirteenth 

 - day 1 after the subject has been placed in the dissecting- 

 room. By that time the upper limbs have been detached 

 from the trunk. 



In form, the thorax resembles a truncated cone. Anteriorly 

 and posteriorly it is flattened ; laterally it is full and rounded. 

 During life the movements of the thoracic walls produce 

 alterations in the capacity of the chest cavity, and play an 

 essential part in the function of respiration ; these movements 

 the student should study upon himself and his friends. 



The thoracic cavity is bounded anteriorly by the sternum 

 and costal cartilages ; it is bounded posteriorly by the twelve 

 thoracic vertebrae and the intervening nbro-cartilages, together 

 with the portions of the ribs which extend laterally from the 

 vertebral column as far as the angles ; the lateral boundaries 

 are formed by the bodies of the ribs, from their angles 

 posteriorly to their anterior extremities anteriorly. These 

 parts constitute the framework of the thorax, and can be 

 studied on the skeleton as well as upon the part before 

 the dissection is commenced. 



The anterior wall of the thorax is shorter than the posterior 

 wall and, during expiration, the upper margin of the sternum 



1 Saturdays and Sundays are not counted. 

 VOL. II 1 



