DUPLICITY. 15 



main arterial trunks. The heart consists of two left hearts 

 united ; there are no pulmonary hearts. Each ventricle 

 gives off an aorta which crosses to the opposite side, so 

 that the heart on the left side supplied the right inferior 

 extremities, and that on the right the left. The carotids, 

 two in number, are given off together from the arch of 

 the right aorta. The trachea is single. The lungs are 

 very small and imperfect ; they probably consist of a 

 single pair. The vessels of the right heart are injected. 

 The palate is deeply cleft. Hunterian. 



70. A similar foetal Pig with the skull and spinal canals laid 



open to show the brain and cords. The adjacent lateral 

 tracts terminate by joining each other, the outer ones 

 alone pass to the brain. Hunterian. 



71. A similar but anencephalous foetal Pig. The base of the 



skull is exposed ; the cerebral nerves are, however, quite 

 distinct at their point of exit from the skull. 



Hunterian. 



72. A foetal Mole with dichotomy of the whole spinal column. 



Hunterian. 



73. A foetal Puppy with dichotomy of the spinal column. The 



median pair of anterior extremities are represented only 

 by a tubercle. It is probable that the dichotomy does 

 not extend into the upper part of the cervical region. 



Hunterian. 



74. A foetal Kitten with dichotomy of the axis and four complete 



anterior extremities. Hunterian. 



75. A similar Kitten. Hunterian. 



76. The skeleton of a similar Kitten, in which the occiput is 



slightly cleft, so that there are two exoccipitals. 



This specimen belongs strictly to the following subdivision, 

 Schizocotis ; it is probable, however, that some of the preceding 

 specimens are similarly affected. It has therefore been thought 

 expedient to separate those forms only as Schizocotis in which the 

 cleft condition of the skull is apparent externally. These divisions 

 are not separated by any distinct lines of demarcation and are 

 purely artificial. The manner in which the median ribs are de- 

 pressed and united in animals affected with dichotomy is well seen 

 in this preparation. 



Presented by J. Burton, Esq. 



