SMIMOVAI, OF THE HEABT. 31 9 



§ 834. Removal of the Heart. — ^For obvious reasons, a cat's 

 heart intended for careful examination should be taken from a 

 large adult. In most cases the same cat may be employed for the 

 removal of the hrain and for the separate study of the abdominal 

 mscera (Chap. VII). Unless the vessels are to be filled with plas- 

 ter, it is better not to bleed the animal, since the presence of the 

 blood in the large veins near the heart facilitates their recognition. 



Instruments and Materials. — Artlnotoine ; tracer ; medium scalpel ; coarse scissors ; 

 bone scissors ; nippers ; coarse and fine forceps ; 6 pieces of linen thread about 20 cm. long ; 

 3 pieces of thick muslin or flannel or chamois leather, each about 15 x 7 cm. ; basin of 

 water and towel ; large tray, with cords for securing the legs of the cat. 



Landmarks. — Prsesternum, xiphisternum and epigastrium (§ 328, Fig. 30, 49, 73, 76) ; 

 clavicle (§ 330, Fig. 30, 73). Observe also the general location of the thoracic viscera in 

 Fig. 77 and 101 and the operations for their exposure (§§ 710, 805). 



§ 835. Exposure. — Divide the skin (§ 599) as directed for the 

 exposure of the thoracic viscera (§ 805), but — unless the lungs are 

 to be employed for study or experiment — begin the longitudinal 

 incision (Fig. 76) dextrad of the prcesternum instead of the larynx. 

 It is also more convenient to make a second transverse incision from 

 the cephalic end of the longitudinal one to or beyond the corre- 

 sponding point upon the left side. 



The triangular or quadrangular area of skin so indicated is to be 

 raised as directed in § 600 and reflected sinistrad. Divide the pec- 

 toral muscles (Fig. 72) on the right by a longitudinal incision par- 

 allel vrith the edge of the skin, taking care not to cut upon the 

 clavicle. Grasp the pectoral mass and dissect it up from the proper 

 thoracic vpall to the meson. Repeat the operation upon the other 

 side and then remove both masses from their attachments to the 

 sternum. Divide each M. rectus tJioracis (Fig. 72, 78) at the caudal 

 transverse cut edge of skin and dissect them up cephalad. 



Through the MM. intercostales on each side near the middle of 

 the exposed area, push the conjoined tips of the coarse forceps, and 

 forcibly separate the blades for about 2 mm. This will permit air 

 to enter the thorax, and the lungs will collapse so as to be in less 

 danger of injury during the subsequent operation. 



With the arthrotome or bone scissors, divide the exposed costi- 

 cartilages close to their junctions with the ribs. Cut across the 

 sternum just cephalad of the xiphisternum, sever the septum medi- 

 astinale and other adhesions to the ental surface of the sternum, 

 and reflect it cephalad with the costicartilages or remove it alto- 

 gether. 



