TERATOLOGY. 



957 



the mouth. In cerebral hernia the chance 

 for the prolongation of life is greater. Some 

 cases are known in which life lasted 20, 

 30, and even 60 years. When complicated 

 with hydrocephalus, puncture has sometimes 

 been instituted, but without success (Earle). 

 Extirpation produced, in another case, in- 

 stantaneous death. 



What are the causes of acrania ? From 

 some of its forms, it is clear that there has 

 been hydrocephalus followed by disruption 

 (Morgagni, Penada, Sandifort, Klein, Otto). 

 In an embryo figured by M. Schroeder Van 

 der Kolk, the summit of the head is extended 

 by hydrocephalus, and has on its superior 

 surface a black gangrenous spot which seems 

 to prognosticate a rupture. 



In another foetus I observed a fissure in 

 the midst of an analogous spot. According 

 to my opinion, the lacerated bags, which are 

 sometimes found on or in the summit of the 

 naked internal surface of the basis cranii, or 

 at the back part of the more developed skull, 

 are caused by such ruptures. Tiedemann 

 gives a description of such a bag, filled with 

 serous fluid, but not yet burst, and situated 

 upon the head of a fetus, which has the ex- 

 ternal appearance of acrania. (Fig. 612.) 



Fig. 612. 



But in those cases in which the flat basis 

 of the skull is only covered with a membrane 

 and with cerebral nerves, in those in which 

 there is a spongy substance upon it, and in 

 those in which the skull, although flat, is 

 otherwise complete, not the least probability 

 exists of the rupture of a cerebral vesicle at 

 an early period of formation. I am able to 

 prove this, I think, by a small foetus of two 

 months, in which the superior part of the 

 skull is wanting, and in which a spongy mass 

 occupies the place of the brain. 



It shows that acrania may also be a pri- 

 mitive malformation, occasioned by the simul- 



taneous malformation of the brain and of the 

 skull. Why I do not impute these malforma- 

 tions to external injury, such as the leaping of 

 a monkey on the belly of a pregnant woman 

 (Sandifort), to a fall down stairs (Pauli), or 

 to the influence of imagination, needs not be 

 demonstrated. 



III. Fissure of the Sack Part of the Body. 



Hydrorachis and Spina bifida. Fissure of 

 the spinal column (spina bifida), and dropsy 

 of the spinal medulla, occur each separately, or 

 connected together. In the highest degree 

 of fissure, the vertebral bodies even are cleft 

 (J. T. Meckel, Tulp, Fleischmann). Fig. 613. 

 represents such a case, after Cruveilhier. 



Fig. 613. 



In a less degree, the vertebral bodies are 

 complete, but their arcs very detective, being 

 completely wanting, or laterally incurved and 

 fused together. In the lowest degree, the two 

 halves of the vertebral arcs are completed, but 

 not united together, so that posteriorly an 

 open space remains between them, and a fis- 

 sure occupies the place of iheprocessus spinosi, 

 which are separated into two lateral and 

 equally incurved parts. 



When this form of fissure of the spinal 

 column is not accompanied by hydrorachis, 

 both parts of the vertebral arcs are not 

 bent laterally, but meet each other so ex- 

 actly, that no open space remains between 

 them. Sometimes the fissure is extended 

 over the whole vertebral column (spina bifida 

 totalis], sometimes it is but partially cleft 

 (spina bifida partialis). The partial fissure 

 occurs more frequently in the lumbar than 

 in the cervical region of the column. The 

 cause of the greater frequency of the partial 

 fissure in the lumbar region is to be im- 

 puted to the termination of the spinal me- 

 dulla in this region ; to its expansion there 



