956 



TERATOLOGY. 



a hernia. The parietal bones are sometimes 

 present, together with flat frontal bones, and 

 a perpendicular occipital bone, so that the 

 summit of the skull is quite closed, with the 

 exception of a small opening. Fig. 609. 

 shows how the malformed cerebral substance 

 is applied to the medulla spinalis. All the 

 cerebral nerves are present. 



This form of monstrosity has in general a 

 less brute-like aspect; the trunk is more 

 evolved, and the whole body in general very 

 heavy. 



Fourth Type. The skull fiat, more evolved, 

 but having an opening, through which the brain 

 protrudes as a hernia. This is what we call a 

 cerebral hernia (hernia cerebri, encephalocele), 

 viz. a tumour covered with the external integu- 

 ments arising from some part of the surface 

 of the skull, and containing a part of the 

 brain. It has commonly the form of a bag, 

 appended to the posterior part of the skull, 

 and resting on the neck. The head is never 

 turned with the face upwards ; the ears do 

 not rest on the shoulders ; the neck is not 

 wanting. The summit of the skull is flat and 

 closed, and its cavity is too small to include 

 the brain, which for this reason is placed on 

 its outside, and backwards. The occipital 

 bone has the form of a vertebral arc, which 

 surrounds the brain, lying at the outside. 

 Fig. 610. shows the external appearance of 



Fig. 610. 



this monstrosity, Jig. 611. the structure of 

 the skull. 



Fig. 611. 



a, frontal ; b, parietal ; c, occipital, bones. 



In many of the published observations, a 

 collection of serous fluid accompanied the 

 hernia cerebri, by which a hydro-encephalocele 

 was formed. 



The situation of the cerebral hernia is 

 in general on the occiput, but sometimes 

 on both sides of the root of the nose (W. 

 Lyon, Kelch) ; above the eye (Adams); on 

 the forehead (Beclard, Saxtorph, Niemeyen, 

 Bredon, Guyenot) ; on the fontanella magna 

 (Held) ; in the parietal bone (Le Dran, Stein, 

 Tren) ; on the glabella, between the orbits 

 (Otto). 



On a survey of these various types, it ap- 

 pears that they all belong to the same class of 

 monstrosities. The nature of the malform- 

 ation is in all the same, namely a defective de- 

 velopement of the skull and of the brain. 

 This takes place in different degrees, so as 

 to convey us gradually from the complete 

 want of brain to those cases in which it is 

 nearly perfect, and differing from the natural 

 condition only in situation. The constancy 

 of form is very interesting in this monstrosity, 

 so that the malformed children resemble each 

 other nearly in every museum, and the pub- 

 lished observations are quite accordant with 

 the cases now occasionally occurring. This 

 proves that the origin of the malformation 

 cannot be accidental. The want of the neck, 

 which is the reason why the ears rest on the 

 shoulders and the chin on the breast, and which 

 gives to this form of monstrosity such a pecu- 

 liar character, is often the consequence of the 

 want of some of the cervical vertebrae (Rathke, 

 Haller, Otto), or of their mutual coalition 

 (Rathke, W. Vrolik), or of their shortness 

 (Sandifort.) As a transition to the brute 

 form, this shortness of the neck is interest- 

 ing, reminding us of the condition of the 

 Cetacea. The prominence of the eyes is oc- 

 casioned by the flatness of the orbits, and 

 by the backward direction of their superior 

 margin. It differs from the manner in which 

 the eyes are prominent in children with internal 

 hydrocephalus. A rich growth of hair is 

 common to all the forms of acrania. Is 

 not this, and likewise the abundance of 

 areolar tissue, to be attributed to a vicarious 

 nutritive function? The frequent absence 

 of the suprarenal glands (Otto), or at least 

 their imperfection and smallness (Morgagni, 

 Hewson, F. Meckel, Soemmering, W. Vrolik) 

 in all acranial foetuses is remarkable. The 

 capacity for persistent life after birth differs 

 according to the different forms of this 

 monstrosity. Acrania does not seem to in- 

 terfere with uterine life. The children who 

 are affected with it are all well nourished, and 

 some of them even very large, at the moment 

 of their birth. Nevertheless, they rarely live 

 longer than a few hours. During this short 

 life they offer some symptoms which are 

 attributable to the reflex action of the 

 nervous system ; such as, for instance, mus- 

 cular contractions when the skin is touched, 

 rejection by the mouth of the recently ex- 

 pressed juice of Pelargonium tomentosum, and 

 the attempt to suck a finger introduced into 



