12 ABNORMAL CONDITIONS OF THE AXIS. 



MS. dissections that there was a third median carotid 

 in front of the trachea,, which divided in the head into 

 two vessels having the usual branches and distribution. 



Hunterian. 



b. Dicephalus, Gurlt. 



In dicephalus the dichotomy extends beyond the base of the 

 skull, and involves the anterior portion of the vertebral column. 



62. The cervical and some of the dorsal vertebrae of a dicephalous 



Calf, in which dichotomy extends as far as the anterior 

 dorsal vertebrae. The atlas and axis of the right neck 

 are unfortunately lost. The dorsal spines below the di- 

 chotomous region are bifurcated. There are two ossinc 

 centres in the bodies of the dorsal vertebrae, a condition 

 seen- in almost all malformations of the spine. A num- 

 ber of small ossinc centres occur between the bodies of 

 the vertebrae at the point of bifurcation. There is a 

 piece of cartilage in the angle of bifurcation. 



Presented by J. B. Stauffer, Esq., 1867. 



63. The brains and a portion of the spinal cord of a dicephalous 



Lamb. Dichotomy extends to an inch and a half below 

 the foramen magnum. 



64. The oesophagus of a dicephalous (?) Lamb bifurcated to within 



about 4 inches of the stomach. 



Presented by R. Partridge, Esq. 



B. Posterior Dichotomy. 



* In Animals. (This condition is almost confined to quadrupeds, and is 

 very rare in the human fostus. Human foetuses affected with di- 

 chotomy have been placed together at the end of the series : see 

 Nos. 87, 88, and 89.) 



a. Dipygus, Gurlt. 



Dichotomy of the posterior portion of the axis is far more 

 common in Mammals than of the anterior portion. There are 

 three distinct forms of posterior dichotomy. In the first the 

 pelvis alone is double and the second axis is wanting ; hence it 

 is doubtful whether such forms should be included in this class. 



