306 report— 1846. 



have been expected from the anthropotomical ideas of the cranial bones, — 

 according to which no one bone is deemed either more or less important 

 than another in its essential nature, and where the squamosal is as little re- 

 garded in the light of a superadded or intercalary piece as the alisphenoid, — 

 that all would be reduced in the same proportion in forming the parietes of 

 the contracted brain-chamber. But this is by no means the case. In the 

 instance above-cited the basioccipital and basisphenoid have been developed 

 to their usual size, and the distance from the posterior boundary of the bony 

 palate to the anterior border of the foramen magnum is as great as in any 

 normal skull. The exoccipitals (condyloid portions of the occiput), the 

 alisphenoids and the orbitosphenoids retain in like manner their full dimen- 

 sions. The distance -between the frontal and temporal bones is as great as 

 in the average of fully developed Caucasian skulls, and is greater than in 

 most of those from the M elan i an race, in which the direct junction of the 

 frontal with the temporal, as in the chimpanzee, is by no means rare. The 

 contraction of the capacity of the brain-chamber is due chiefly to arrested 

 development of the frontals, parietals, supraoccipital and squamosals. By 

 the reduction of the supraoccipital and the retention of the centrums of the 

 cranial vertebrae of their normal proportions, the foramen magnum becomes 

 situated nearer the back part of the basis cranii than in the normal skull. 



In a still smaller cranium of a female idiot, who reached the age of twenty- 

 one years, which is preserved with the male idiot's skull above-mentioned in 

 the anatomical museum of St. Bartholomew's Hospital, the contrast between 

 the normal proportions of the basioccipital, basisphenoid, exoccipitals, ali- 

 sphenoids and orbitosphenoids, on the one hand, and the reduced dimensions 

 of the supraoccipital, parietals, frontals and squamosals on the other, is still 

 more striking and significant of the true nature of those bones. The normal 

 growth of the centrums, indeed, might be explained by the concomitant nearly 

 normal size of the medulla oblongata, base of third ventricle and optic chi- 

 asma, in the brain of the same idiot : but it is not so obvious from the con- 

 dition of the brain itself why the alisphenoid should not have shrunk in the 

 same proportion as the parietals, frontals and squamosals. To the nomologist, 

 however, the recognised difference of subjectivity to modification presented 

 by the neurapophyses, spines and diverging appendages of the typical seg- 

 ments, renders very intelligible the partial seats of arrested growth in the 

 bones of these idiots' crania. 



In reference to disease, also, one sees not why the alisphenoid should have 

 a minor attraction for the morbid products deposited, or be less subject to 

 the destructive actions excited, during syphilitic or mercurial disease, than 

 the parietals, or the orbitosphenoids than the frontals, or the exoccipitals 

 than the supraoccipital : yet it needs but to examine any series of such 

 morbid skulls in our museums of pathology to be convinced that the variable 

 and peripheral elements of the neural arches, viz. their expanded spines, are 

 almost exclusively so affected : the frontal and parietal being the most 

 common seats of the disease ; the supraoccipital a less frequent one, concomi- 

 tantly with its minor deviation from the typical standard of the element. I have 

 yet seen no example in which either a cranio-vertebral centrum or neura- 

 pophysis was so affected ; but the nasal bones are notoriously attacked. 



It would be easy to multiply such instances of the new light — new eyes, 

 so to speak, — with which human anatomy, normal and abnormal, is viewed, 

 after the essential nature or general homology of the parts have been appre- 

 ciated. 



If the bones 4, s, 12, fig. 5, have been correctly determined as the parapo- 

 physes of the cranial vertebra?, they might be expected to be subject in the 



