328 



STUDY OF PIG EMBRYOS. 



each side a fold, Plx, which projects into the cavity of the lateral ventricle. This 

 fold contains in its interior a prolongation of the mesodermic tissue of the falx, 

 and it is covered by a continuation of the wall of the hemispheres. The covering 

 layer of the fold is much thinner than any other portion of the brain-wall shown 

 in the section, and shows no differentiation into layers. It retains throughout 



Fx. ec.gl. 



H. 



L.V. 



Plx. 



C.str. 



m.rec.sup. 

 m.retr.b. 



hy.gl. 



art. 



FIG. 221. PIG, 20 MM. FRONTAL SECTION or HEAD. SERIES 40, SECTION 123. 



arach, Arachnoid zone, art, Lingual arteries. C.str, Corpus striatum. ec.gl, Ectoglia. Fx, Falx cerebri. H, 

 Cerebral hemisphere, hy.gl, Hyoglossal muscle. L, Lens. L.V, Lateral ventricle. Mk, Meckel's car- 

 tilage, m.rec.sup, Musculus rectus superior, m.retr.b, Musculus retractor bulbi. m.r.lat, Musculus rectus 

 lateralis (cf. text). Mx.i, Inferior maxillary nerve. ' Ph, Pharynx. Plx, Plexus choroideus lateralis. Ret, 

 Retina. Sk, Anlage of membranous skull. Ton, Tongue, x, Unidentified structure. X 18 diams. 



life an epithelial character and is already to be termed ependyma. The ependyma 

 of the two folds is connected across the median line, and it forms the median 

 dorsal boundary of the cavity of the fore-brain. The two folds are the anlages 

 of the lateral choroid plexus. They are destined to grow much in size and in 

 complexity of form, but they always remain morphologically what they now are, 



