164 CAVERNOUS TUMOURS. 



trabecule at right angles to their length, would, if they con- 

 tracted, diminish the islets of the parenchyma of the other net- 

 work, whose trabecul^e would in their turn become shorter and 

 thicker. Fibres Avhich correspond in their direction to the long 

 axis of the trabeculse of one of the two networks, would, if they 

 contracted, increase the size of the islets of the parenchyma of 

 the other network and render its trabecule© thinner. 



We may also suppose the entire mass of a trabecular network 

 partitioned out into trabecular substance proper and tetrahedral 

 or cubical nodal pieces (connecting pieces, Yerbindungsstiicke), 

 common to three or four contiguous trabeculse. Supposing the 

 joint yolume of the two networks to remain constant, and the 

 trabeculse of one network to become longer and thinner, this 

 would necessarily entail on the one hand a diminution in the 

 size of their own nodal pieces, on the other a shortening and 

 thickening of the second network whose nodal pieces would 

 simultaneously increase in size. 



When once w^e haye thoroughly grasped these rather difficult 



stereometric conceptions, we get at a yery natural theory of the 



mechanism of cayernous metamorphosis. True, it is far from 



easy to conceiye of a parenchyma traversed by an ordinary 



vascular network as being made up of a system of rounded 



trabeculse enclosing meshes between them. This is made easier 



Fig 53 ^^ imagining several vessels seen in transverse 



section (fig. 53^) ; the dotted curves (which may 



at the same time be supposed to represent the 



^ — '^ / \ lines of contact of the capillary arches between a 



\''^>.^ \ ' and a) would then indicate the transverse sections 



""""'^k of the trabeculse of parenchyma. The vascular net- 



^^ work would thus be made up of long trabeculse and 



small nodal pieces, the parenchymatous network of very thick 



but extremely short trabeculse and nodal pieces of colossal size. 



Now the cavernous metamorphosis is brought about as 

 follows : in a circumscribed part of an organ, embryonic tissue- 

 is converted into spindle-cell tissue and fibroid connective tissue 

 along the course of the vessels ; this is folloAved by contraction 

 taking place at right angles to the axis of the parenchymatous 

 trabeculse, in the direction therefore of the dotted curves (fig. 

 53), causing elongation of the trabeculse, diminution in the 

 size of their nodal pieces, and, as a necessary consequence^, 



