DEVELOPMENT OF THE CHOROID PLEXUS 



95 



The lateral choroid plexus (fig. 21, p.c.v.l.) is of considerable 

 size, but does not nearly fill the ventricle (fig. 11, p.c.v.l.). In 

 antero-posterior extent the plexus measures 1.55 mm., the ven- 

 tricle measuring 2.97 mm. The anterior end of the plexus is 

 much the larger and is less folded. Thompson ('09) has de- 

 scribed a similar condition in the cat. The attachment of the 

 plexus to the roof plate is now much narrowed, owing to the 

 relatively small size of the paraphysal arch (fig. 20, p.c.v.l., p.a.). 

 The taenia fornicis is now closely approximated to the taenia 

 chorioidea, the fissura chorioidea being reduced to a narrow 



11 



12 



Fig. 11 Section throuuli tlif iliciKophaloii of the L'S nun. embryo, H'.)l. 

 X61. Slide 24. Sect. 318. 



Fig. 12 Section througli the (licnccphalon of the 32 mm. emliryo. 1141. 

 X OL Slide 24, Sect. 2. 



slit (fig. 11, /.r.). In its growtii, the j)lexns has extended some 

 0.25 mm. anterior to its point of attachment to the mid-line of 

 the telencephalon. The connective tissure resembles that of the 

 19 mm. embryo closely, except that the cells are farther apart, 

 but the ependymal layer has become much thinner and consists 

 clearly of a single layer of columnar cells, with the nuclei in the 

 ends of the cells next the ventricular cavity (fig. 28). The 

 epend\^ma of the posterior j^art of the plexus resembles more 

 closeh' that of the 19 mm. embryo, there being several layers of 

 irregularly arranged nuclei. The posterior part of the plexus 

 is much attenuated and much more folded than the anterior end. 



