VARIATION. 87 



from the posterior part of the arch of the aorta, and 

 passes behind the oesophagus to its destination. 



From the Museum of Sir A. Cooper, Bart. 



375. A portion of the arch of a Human aorta. The vertebral 



arteries are given off between the innominate and left 

 carotid arteries. The right vertebral is considerably 

 larger than the left. 



b. Situs Mutatus. 



376. A large Human heart with all its parts reversed; there 



was also reversion of all the viscera. The systemic auricle 

 and ventricle are enormously enlarged and hypertrophied. 

 The coronary sinus is largely dilated and receives two 

 large veins. There is no evidence that the hypertrophy 

 and dilatation are due to the malformation. These 

 changes are the results of disease. The spleen in this 

 case was divided into nine separate glands (see No. 390). 

 The specimen is described and figured in the Path, Soc. 

 Trans, vol. xx. p. 93, pi. v. 



Presented by Dr. Hickman, 1871. 



c. In the number of arterial valves. 



Sometimes two or four valves exist at the mouth of the aorta 

 or pulmonary artery. With our present knowledge it is perhaps 

 best to consider these deviations as variations. There is no 

 evidence of dichotomy in cases of supernumerary valves. The 

 condition is not very rare. 



d. Division of the cavity of a ventricle by an adventitious septum. 



This condition is perhaps a very near approach to excess of 

 development. In the following preparation, however, it is 

 apparently due to a variation in the development and position 

 of the columnse carnae. 



377. An adult Human heart with a strong muscular septum 



dividing the apex of the right ventricle into two cavities. 

 The septum terminates in a concave margin between the 

 pulmonary artery and the tricuspid valve ; it apparently 

 consists of united columnse carnse. It is perforated by 

 numerous small openings, between the muscular bundles 

 of which it is composed. Hunterian. 



