Fig. 177.—Lesions of exudative pericarditis produced by a foreign body. Relation of the pericardium to the sternum and ensiform cartilage. Pericardium opened. D, diaphragm; Œ, œdema of the dewlap, Ax, ensiform cartilage; F, liver; Vb, gall bladder; 1, posterior lobe of the lung, drawn backwards; 2, cardiac lobe; 3, anterior lobe; E, spot where the foreign body penetrated, towards the point of the pericardium, between the neck of the ensiform cartilage and the circle of the hypochondrium.
A glance at the annexed diagram (Fig. 177) will show this.
The diagram, carefully reproduced from an anatomical preparation of an animal which succumbed to pericarditis, shows that the distended pericardium extends close to the neck of the xiphoid cartilage.
First stage. Identify the three following anatomical guiding points:—
(1.) Xiphoid appendix and white line. (2.) Point at which the circle of the hypochondrium becomes attached to the sternum. (3.) Point at which the external mammary vein penetrates the abdominal wall (Fig. 178).
Lines uniting these three points enclose a right-angled triangle, which the operator must imagine to be bisected by a third line.
The incision, which should be about 8 inches in length, follows this bisecting line at an equal distance between the white line and the circle of the hypochondrium, to a point within about 8 inches of the anterior margin of the mamma. All these points are readily observable before the animal is cast.
Fig. 178.—Seat of operation for puncturing the pericardium by way of the ensiform cartilage. L B, White line; H, line of the hypochondrium; V. M.a., anterior mammary vein; P, point where the pericardium is punctured through the incision.