22 Practicum III. The Cat's Heart. 



The duct and nerve are better demonstrated upon freshly killed ani- 

 mals ; see Anatomical Technology, Figs. 103, 107, 108. 



$ 34. Make a drawing of the left thorax similar to PI. VII, but shade very lightly if 

 at all. 



35. With the coarse scissors or nippers transect the sternum near 

 the diaphragm ; also the first ribs ; then the intervening soft parts so as 

 to remove the sternum. One or more vessels may be seen passing from 

 the great thoracic vessels to the sternum. With the tracer tear the pleura 

 and connective tissue so as to expose the aorta and esophagus more fully. 



36. Opposite the apex of the heart slit the aorta lengthwise and in- 

 flate it cephalad so as to demonstrate the following points : 



a. The aorta extends cephalad and then turns somewhat sharply to the right and then 

 caudad to join the base of the heart. Starting from the heart, therefore, the arch so 

 formed is to the left, and the vessel itself is at the left rather than the right of the meson ; 

 Anatomical Technology, Fig. lor. 



b. With all Mammals the aortic arch is left ; with all Birds it is right ; see the con- 

 trasted injected preparations in the Museum ; the matter is further discussed in the 

 lectures. 



c. From the aortic arch spring two great arterial trunks carrying blood to the head 

 and arms. 



d. If time permits expose them with the tracer ; the "names and divisions are given 

 in Anatomical Technology, Figs. 91, 101, 102; compare with the human arrangement as 

 seen in the wall maps. 



37. Slit the aorta to near the diaphragm and note the orifices of the 

 ten pairs of INTERCOSTAL ARTERIES. 



38. Cut the phrenic nerves, aorta and postcava about 2 cm. from 

 the diaphragm ; then the precava, azygous vein and branches of the aortic 

 arch. Pull all the parts cephalad, divide the pleural attachments with 

 the scissors, and remove. 



39. The Cat's Heart and Great Vessels. If time permits a hasty examination of 

 these may be made as follows, but the beginner will find the sheep's heart more easy to 

 dissect. 



a. With the fingers tear off any fragments of fat or thymus ; then 

 the esophagus ; then the trachea with its branches, the BRONCHI ; cut the 

 bronchi near the lung-remnants. These latter are probably connected 

 with the heart by the PULMONARY ARTERIES and VEINS. The veins may 

 be full of blood. 



b. Cut the pulmonary vessels close to the lung-remnants so as to 

 free the latter. 



40. Removal of the Pericardium. a. At about the middle of the 

 entire length of the organ pinch up a fold of the membranous sack which 

 incloses it ; slit the sack and remove, trimming quite closely to its attach- 

 ments at the base, but without cutting the heart itself or the vessels. 



a. The place and manner of attachment of the pericardium may be more easily ob- 

 served in the sheep ; the object of this removal is to expose more fully the regions of the 

 heart and the vessels. 



41. Right Aspect of the Heart. a. Place the heart in the posi- 

 tion shown in PI. VII, the right side toward you, the apex toward your 

 right. 



b. Recognize the RIGHT AURICLE and VENTRICLE ; both are probably 

 quite firm to the touch on account of the contained coagulated blood. 



c. Note the attachments of the three great VEINS which bring blood 

 to the auricle, the POSTCAVA and PRECAVA and the RIGHT AZYGOUS. 



42. Left Aspect. Turn the heart upon its right side and see that 

 the vessels lie in what seems to be their natural positions. 



