294 MANUAL OF EQUINE MEDICINE. 



parietal, are, as a rule, considerably deformed and thrown 

 out of their natural direction, and in places so expanded and 

 rarefied as to be no thicker than tissue paper. When the 

 internal distension has been very considerable, their borders 

 do not meet as in their normal condition, but are often 

 widely separated, leaving between them vast fontanelles, 

 occupied only by a thin translucent membrane, the dura 

 mater, which is in immediate contact with, and closely 

 adheres to, the skin. 



' In some instances, especially in the calf, the bones on 

 their upper part do not join at all, and the roof of the 

 cranium, or rather of the cranial tumour, is entirely absent. 

 In other instances, and particularly in the foa], a kind of 

 bony arch extends from the nasal to the occipital bones, 

 in the direction of the sagittal suture, with only here 

 and there, on each side, small osseous patches from the 

 parietal or temporal bones, and adhering to the dura 

 mater. 



' The tumour is always entirely covered by intact, though 

 sometimes very thin skin, to which the hair is ordinarily 

 attached, and is, indeed, at times longer than usual, espe- 

 cially at the sides. 



' Owing to the great development of the forehead, the 

 upper jaw appears to be shorter than usual ; and, indeed, it 

 will be found that it is really so.' 



2. General Symptoms. — In the early stages the animal is 

 irritable, and manifests febrile symptoms. Afterwards the 

 foal becomes weak and debilitated, and its sensibility 

 becomes impaired. Paralysis, coma, and convulsions pre- 

 cede death in fatal cases. 



When hydrocephalus comes on in adult life, the symptoms 

 are occult ; but fortunately this disease is of rare occurrence, 

 except as a congenital defect. 



Prognosis. — Cases of recovery from congenital hydro- 



