THE HEART. 



323 



liquid or vapour constantly exists. The serous membrane is 

 smooth, and covered by delicate epithelial cells. (Fig. 109.) 



Fig. 109. Tesselated epithelium from 

 pericardium of sheep. Fusiform cells 

 are shown, such as are constantly seen, 

 especially in young animals. 



On examining the heart when removed, with its large ves- 

 sels, as seen in the annexed Figs. 110, 11 1, it is found divided 



Fig. 110. (CHAUVEAU.) The heart and principal vessels, seen from the left side; 

 a, Right ventricle; 6, left ventricle; c, right auricle; d, left auricle; e, pulmonary artery. 



