THE NERVOUS SYSTEM. 781 



it is never so great s,s in congenital hydrocephalus, and is not accompa- 

 nied by the changes in the shape of the skull which form so prominent a 

 feature in the latter disease, since the bones are firmer and the sutures 

 united. In this form of chronic hydrocephalus the changes in the epeii- 

 dyma above described are usually more or less well marked, and they 

 may be associated with the production of fibrin and pus. 



3. PRIMARY HYDROCEPHALUS IN ADULTS. The conditions leading 

 to this form of lesion are not understood. It is apt to occur in persons 

 over thirty years of age. Sometimes one, sometimes both lateral ven- 

 tricles are dilated. The dilatation is usually moderate, sometimes very 

 slight, and never as great as in congenital hydrocephalus. The ven- 

 tricles usually contain transparent serum, and the ependyma is thickened 

 and roughened. In some cases it is the only lesion found to account for 

 the death of the patient. 



TUMORS. 



New formations of connective tissue in the ependyma, although usually 

 diffuse, may be circumscribed and form small, projecting connective-tis- 

 sue nodules, which may be reckoned among the fibromata. Small fibro- 

 mata are sometimes detached from the walls of the ventricles and lie free 

 in the cavity. Small lipomata, angiomata, and also sarcomata and glio- 

 mata occur rarely. Chondromata and angiomata may occur in the choroid 

 plexus, the latter sometimes being as large as a hen's egg. The choroid 

 plexus is not infrequently the seat of transparent cysts, usually of small 

 size ; they may contain a clear fluid, or colloid material, or droplets of 

 fat, or calcareous particles. A small dermoid cyst containing hairs has 

 been described. The cysts have no special pathological significance. 



Primary carcinomata sometimes involve the ventricles. 



The calcareous bodies called brain sand ' (see Fig. 501), occur fre- 

 quently in the choroid plexus, and corpora amylacea may occur here and 

 beneath the ependyma. 



PARASITES. 



Cysticercus and echinococcus cysts are sometimes attached to the walis 

 of the ventricles or may be free in their cavities. 



The Brain and Spinal Cord. 



Malformations of the Brain. 



CYCLOPIA. This malformation consists in an arrest of development affecting ths 

 cerebrum, which, instead of separating into two hemispheres, remains single, with on^; 

 ventricle, and the rudiments of the eyes usually become joined and form one eye. This 

 single eye is in the middle of the face, near the place of the root of the nose, in a single 



1 The little, hard masses called brain sand consist of aggregations of small particles 

 of carbonate and phosphate of lime with a small amount of phosphate of ammonia and 

 magnesium. With these there is more or less organic matter 



