TRANSECTION OF A MAMMAL. 



43 



It is often desirable to describe the place of origin or insertion of muscles 

 as from or upon a given fraction of the entire length of a long bone. When 

 the area extends over a third of the whole length the thirds would be 

 designated usually as proximal, middle or distal; but when fourths or 

 smaller subdivisions are employed, they may be designated as first, second, 

 etc., as shown upon the femur in Fig. 6. 



Dorsal aspect 



muralis 

 n> 

 it a 



-aorta. 



.Track sa 



.puLmo {Lung) dexter 



Ventral aspect 



~~~meaia.srinale 

 '-Sternum 



FIG. 7. DIAGRAM OF AN IDEAL TRANSECTION OF THE THORAX OF THE CAT, WITH 

 THE ARMS IN AN APPROXIMATELY NORMAL POSITION, AND SHOWING THE 

 LOCATION OF THE PRINCIPAL VISCERA. 



89. In Fig. 7, the cut surface is viewed from the caudal aspect, so that 

 the right and left parts are as in the other diagram (Fig. 6). 



As a whole, the body is symmetrical, the two halves being reversed repe- 

 titions of one another on opposite sides of the meson. 



No definite separation exists between the dorsal and the ventral regions. 

 We may, however, speak of the dorsal and the ventral aspects, and the 

 vertebral column, or main axis of the soma, intervenes between the dorsal 

 cavity, or Canalis neuralis, and the ventral cavity, the ccelum, whose more 

 cephalic division or thorax is here transected. 



The Canalis neuralis contains the myelon, and the coelum the organs of 

 organic life, the thoracic, abdominal and pelvic viscera. 



The following parts and organs are mesal or approximately so, at least 

 in the embryo : nose, tongue, myelon, centra vertebrarum, aorta, oesophagus, 

 trachea, heart, sternum. 



The following are in pairs: eyes, ears, kidneys, costcs, costicartilagines 

 (costal cartilages), pulmones (lungs), pleura, limbs. 



The right lung is shown as a single and simple sack, communicating 



