THE ANATOMY OF THE CHIMPANZEE. 43 



case, that of Chapman, there was a sliort left innominate for the left carotid and sub- 

 clavian. Dr. Keith remarks: " Such an oi-igin for the left carotid will probably be found 

 to occur as a prevailing variation in the chimpanzee, for in another individual of 

 that genus an approximation to that condition was observed." The last words express 

 precisely the case of " Gumbo." 



Inside of heart. The right auricle much as in man. There is a well-marked 

 annulus ovalis. The fenestra is completely closed. There is no remnant of an 

 Eustachian valve, but on the right wall there is a long, slightly raised valvular fold 

 separating the smooth part of the cavity from that part of the anterior wall bearing the 

 musculi pectinati. The fold starts from the right side of the opening of the coronary 

 sinus and runs upward and forward on the outer wall with an anterior concavity. The 

 greatest height to which the valve could be raised from the wall could hardly exceed 

 3 mm. Its function, at most a very slight one, must be to hinder the regurgitation of 

 blood towards the atrium. 



The feft auricle shows a lunated depression on the septum. The walls are smooth 

 except in the appendix which is smaller than the right one. 



The walls of the right and left ventricles present about the relative thickness 

 observed in man. The cavity of the right ventricle is traversed about half way up by a 

 muscular moderator band some 3 mm. in diameter. The three parts of the tricuspid 

 valve are not very easily distinguished. There is a large right one and a large septal 

 one which meet behind. A small infundibular segment might be reckoned a part of the 

 right one. The inside of the right ventricle presents a great development of columnae 

 carneae. The interior of the left ventricle is striking. The surface of the septum is 

 perfectly smooth except near the apex. The outer side presents a wonderful network. 

 The mitral valve is as in man. 



The great arteries were not split open, so that the valves cannot be thoroughly 

 examined. They apparently are not remarkable. 



The Arteries. 



The axillary artery gives off an anterior and a posterior circumflex which arise from 

 a! common trunk. The posterior runs round the neck of the humerus as in man, with the 

 circumflex nerve. It sends a branch down the back of the arm between the external and 

 the long heads of the triceps. 



The brachial artery runs as in man. It gives off almost at its origin a branch 

 which supplies the inside of the arm and another which luns with the niusculo-spiral 



