584 



Harris Hawthorne Wilder 



mobion, but belong to the separate individuals and lie upon the sides of 

 the two sets of thoracic viscera, their ventral aspects facing the median 

 oesophagus. An aorta and a posterior vena cava, each individual, run 

 down the ventral aspect of each. 



The two sets of thoracic viscera are separated from one another by 

 a partition of pleura, forming two thoracic cavities, the larger one as- 

 sociated with the perfect, the smaller with the synotic side. The parti- 

 tion is, however, placed obliquely with reference to the compound thorax, 

 so that the large chamber occupies not only the space immediately l^ehind 

 the sternum of the perfect side, but also that framed in by the vertebral 

 column and ribs of component B : the smaller thoracic cavity is simihirly 

 related to the synotic side and component A. The results of the dis- 



Ant. Vena Cava. 



0*^ 



Fig. 10. 

 attached. 



Baldwin Syiiote, Teras III. Heart of perfect side, with lungs 



sections of these chambers and their organs may be treated separately, 

 l)earing in mind the composition of each set of viscera. 



The heart and lungs of the larger chamber, that of the perfect side, 

 are exposed by laying back the sternum and costal cartilages of this 

 side [Fig. 10]. They appear nearly normal, so much so in fact that it 

 seems pfobable that the slight deformation they display has been due to 

 development in too cramped surroundings, and that they must have been 

 entirely normal at an earlier stage of development. The heart is large, 

 with well defined auricles and ventricles in normal relation. Upon the 

 sides of this organ, and partly adherent to it, lie the lungs, rather in- 

 complete in their development, 1)ut normal in respect to the number of 

 lobes, the right (A's) with three, the left (B's) with two. The large 



