been observed (G. Vrolik, Rudolphi). See fig. 615.
Internal hydrocephalus has always a pre judicial influence upon the condition of the rest of the body, principally upon its nutrition and upon the osseous system, which it pre disposes to emollition. It has a very great influence on the bones of the skull. Its effects are : a. A large expansion of the skull, whilst the face preserves its common shape, and is in great disproportion to the enormous cir cumference of the skull. This disproportion is the most significant symptom of hydroce phalus, and distinguishes it from simple am plification of the head.
b. A protuberance of the frontal tubero sities, which is to be considered as an arrest at an early period of developement, occasion ing an enormous augmentation of the facial angle, which greatly exceeds a right angle.
c. A pushing downwards of the orbital parts of the frontal bone, which makes the superior orbital margins to disappear totally, and to form a protuberance with the frontal part of the frontal bone. The eyes thence acquire a strange direction, their axes being turned upwards.
d. A-symmetry of the hydrocephalous head, which is always more or less oblique. This is the effect of the unequal expansion of the brain. To this may also be ascribed the strange form which the skull acquires when it is regularly extended and developed on its fore and lateral parts, whilst the occiput has a very singular prominence. Such a form is, without doubt, occasioned by a regular expansion of both the hemispheres of the brain tip- and sidewards, whilst their posterior lobes and the cerebellum have preserved their regular form. The parietal bones are thereby expanded and augmented in circumference, whilst the occipital bone, not participating in the expansion, is disproportioned to the rest of the skull. The parietal bones are removed from it, so that, during the primitive ossifica tion, an interval is formed, which is after wards filled up with Wormian ossicles.
Not less singular is the form of the head and skull, when, probably on account of the position of the head in the womb (as is the case in a partus pedibus prwviis), the pressure of the fluid has been exercised principally downwards, so as to extend chiefly the lateral parts of the head.
e. An abnormal disposition of the cranial bones. The fontanellm acquire, in the first instance, a very large dimension, and some parts of the cranial bones remain cartila ginous, which parts are, in a more advanced period, filled up with Wormian ossicles.
Baillie asserts, that sometimes the already formed sutures are opened by the serum exuded in hydrocephalus internus. In other cases, the want of closure of the sutures is to be imputed to a too great thinness of the bones.
2. Hydrocephalus externus is by some (Mon ro, Wrisberg, Hartell) erroneously considered as the result of hydrocephalus internus, followed by laceration of the cerebral hemispheres.
It is proved, by a great many observations, that such a laceration occurs very seldom. The fluid is, in most cases of hydrocephalus externns, exuded on the surface of the brain. This may be the consequence of an arrest of developement, as I observed in a cyclopic lamb, but it may also be produced by inflamma tion. The serum is accumulated between the dura mater and the skull, or between the two layers of the arachnoid membrane, but in most cases its situation is between the dura mater and the arachnoid membrane. In all these cases the brain is strongly compressed, shrunken, and hard (Kaltschmidt). Dullness and somnolence are, according to Frank, the consequences of hydrocephalus externus, and convulsive affections those of hydrocephalus internus.
V. Acephali, or Foetus without a Head.
When we observe the foetus in its first periods of developement, the head is not yet clearly distinct from the trunk. From the third to the fifth week of gestation, the head, not previously discernible, grows so rapidly, that it has in the fourth week acquired the same volume as the trunk. Now the de velopement of the foetus is sometimes arrested at that early stage when the head is not yet distinguishable ; the result of such an arrest must manifestly be an acephalus. This de nomination is, again, as erroneous as many others ; for not only the head, but many other parts, are wanting. The question re mains whether a more appropriate name could be given. Gurlt tried to do so, but, I fear, not with good success. He calls the lowest form of acephali aniorphus globosus, which is a true contradictio in adjecto. I think it there fore proper to preserve the old name of acephali, to which I refer, as has been done by Tiedemann and G. Vrolik, nine types, for which I think it not necessary to give special names.