4 QUATERCENTENARY STUDIES IN PATHOLOGY 



To understand the nature, structure and primary connections of the 

 bulbus cordis, one must study this chamber of the heart in fishes, of the 

 shark or allied tribes, in which it reaches its highest structural and 

 functional development. It is the last of the four pulsating chambers of 

 the primitive vertebrate heart. In figure i, these four chambers are 

 shown, the sinus venosus (i), a reservoir into which the great veins 



Figure i, heart of Xiphias gladiuSy showing the four primary compartments of the heart 

 (from a specimen in the Museum of Royal College of Surgeons, England). 



(i) Sinus venosus. 



(2) Auricle laid open, showing the venous valves guarding the orifice of the sinus. 



(3) Auricular canal. 



(4) Ventricle. 



(5) Bulbus cordis. 



(6) Lower orifice of bulbus (ventricular orifice). 



(7) Upper II (aortic orifice). 



(8) Common ventral aorta leading to gills. 



discharge their blood, the common auricle (2), the essential function of 

 which appears to be that of loading the ventricle ; the common ventricle 

 f^), and the bulbus cordis (5), out of which opens the primitive ventral 

 aorta leading to the bronchial circulation. It is a matter of regret that 

 there is so little direct experimental evidence of the exact part played by 



(58) 



