PHYSIOLOGY: PRACTICUM III: PLATE VII. 



THE CAT'S THORAX AFTER THE 



REMOVAL OF THE RIGHT LUNG. 



The viscera are undisturbed excepting that the three principal lobes of the right lung 

 have been amputated. The large black spot on each root-section represents the BRON- 

 CHIOLUS ; the smaller the lesser AIR-TUBES, and the branches of the PULMONARY 

 ARTERY and VEIN, without distinction. The heavy lines surrounding each root-section 

 represent the PLEURA ; the light extension from the third or caudal root is an exagger- 

 ated indication of the fact that here the two layers of pleura are unseparated by lung sub- 

 stance and constitute a MESOPNEUMON (Mpn). The fourth or AZYGOUS LOBE lies 

 in a recess, partly covered by the POSTCAVA ; the part ventrad of (above in the figure) 

 the postcava is shaded a little darker to indicate that it is seen through not only its own 

 layer of pleura but also the two layers forming the lateral wall of the recess. The extent 

 of this recess is indicated upon the diaphragm, Plate VIII. The THYMUS BODY is shown 

 large, as it is in young cats. The interval between the STERNUM and the thymus and 

 HEART is shaded to represent two conjoined layers of pleura constituting the THORACIC 

 SEPTUM. These layers diverge to extend either way upon the ventral and lateral walls 

 of the thorax as the PARIETAL PLEURA ; the heart and the thymus are also between 

 two layers, but the outlines of these and indeed of all the other organs have been so 

 sharply defined in the figure that the continuity of the visceral pleura over them is not 

 well illustrated. 



The heart is still covered by the PERICARDIUM, but the VENTRICULAR and 

 AURICULAR portions are distinguishable ; the latter joined by three VEINS, the POST- 

 CAVA, PRECAVA and RIGHT AZYGOUS. (On the figure this last word is misspelled 

 azyous). Upon the two cavas and intervening auricle lies the right PHRENIC, the motor 

 nerve of the diaphragm, seen also cephalad of the first rib. 



