TERATOLOGY. 



959 



Brain of a new-lorn Lamb with Cyclopia. 

 a, a, medullary expansion filled with serous fluid ; 

 b, optic nerve ; c, e, peduncles of the brain ; d, pons 

 varolii; e, medulla oblongata; /,/, cerebellum; 

 g, spinal medulla; 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, the 

 cerebral nerves, existing besides the optic nerve. 



been observed (G. Vrolik, Rudolphi). See 

 fig. 615. 



Fig. 615. 



(Altered from Rudolphi by W. Vrolik.) 



Human Ovum, with an Embryo of two months, affected 

 with hydrocephalus. 



Internal hydrocephalus is, however, not 

 always occasioned by arrest of develope- 

 ment in an early period of formation, but 

 may be produced by chronic inflammation, 

 (G. Vrolik), to which the child is, without 

 doubt, as much subject during uterine life 

 as after its birth. The principal causes of it 

 seem to be external injuries suffered by the 

 pregnant woman, and sometimes even reite- 

 rated contact by the act of copulation, if the 

 pelvis is large, and the womb seated very 

 low. Pseudo-membranes are on this ac- 

 count often found on the internal surface of 

 the expanded ventricles (G. Vrolik), by which 

 the deposition of the serous liquor may be 

 limited to one or more of the cerebral ven- 

 tricles, so as to produce an a-symmetrical 

 expansion of the head ; this is, on the con- 

 trary, symmetrical, if both the lateral with 

 the third and fourth ventricle are equally and 

 universally extended by the fluid. The head 

 acquires, in such case, an enormous, but sym- 

 metrical, volume (E. Sandifort, W. Vrolik). 

 The slower such a secretion of fluid takes 

 place, the slower the head increases in volume, 

 and the less it endangers life, and the less 

 the free evolution of the mental faculties 

 is interfered with. Some cases are men- 

 tioned, in which life lasted sixty years 

 (G. Vrolik), thirty years (Michaelis), and fifty- 

 four years (Gall). It is remarkable that in many 

 of these cases, neither the senses nor the 

 intellectual faculties were in the least im- 

 paired. This proves that the substance of 

 the brain is not altered by it, and that the 

 form only of the brain is changed by the 

 unfolding of its convolutions. This unfolding 

 is the consequence of the pressure which 

 the fluid exercises from the inside towards 

 the outside, and of the thereby augmented 

 volume of the ventricles (Hunauld, Gall). 

 Those who presume that through the influ- 

 ence of the serum exudated in the ven- 

 tricles the dissolution and even the total de- 

 struction of the cerebral substance may be 

 effected, go evidently too far (Cruveilhier). 

 However large may be the surface into which 

 the hemispheres of the brain have been un- 

 folded, the white medullary substance can 

 always be distinguished from the grey 

 (G. Vrolik). The parts contained in the 

 ventricles are sometimes intact (G. Vrolik), 

 but sometimes incompletely developed, and 

 what we should call depressed (Aurivillius, 

 Biittner, Malacarne, Klein). The corpus 

 callosum assumes a thin lamellar form; the 

 septum pellucidum and the fornix become 

 thinner ; the glandula pituitaria and pinealis 

 deviate in general from their natural condition 

 (Friend, Malacarne, Wrisberg). The cerebral 

 nerves are in general not changed, and the 

 cerebellum is in most cases natural. The 

 lumen of the cerebral arteries is commonly 

 very large (Biittner), and Friend saw two in- 

 ternal carotids passing through the carotid 

 canal of the right side. In a few cases there 

 was observed a degeneration of the cerebral 

 substance, which resulted in a deranged and 

 feeble state of the mental faculties (Biittner). 



