284 OSTEOLOGY. 



thoracic region they can best be studied in their simplest form ; here the ribs which Gegenbauer 

 regards as a differentiation from the inferior or haemal arches, in opposition to the view advanced 

 by others that they are a secondary development from the fibrous intermuscular septa articulate 

 with the transverse processes and bodies of the thoracic vertebrae through the agency of the 

 tubercular (diapophyses ) and capitular (parapophyses) processes respectively, the latter being 

 placed, strictly speaking, on the vertebral arch behind the line of the neuro-central synchondrosis. 



An interval is thus left between the neck of the rib and the front of the transverse process ; 

 this forms an arterial passage which corresponds to the foramen transversarium in the transverse 

 processes of the cervical vertebrae, the anterior bar of which is homologous with the head and 

 tubercle of the thoracic rib, whilst the posterior part lies in series with the thoracic transverse 

 process. These homologies are further emphasised by the fact that in the case of the seventh 

 cervical vertebra the anterior limb of the so-called transverse process is developed from an 

 independent ossific centre, which occasionally persists in an independent form as a cervical rib. 



In the lumbar region the lateral or transverse process is serially homologous with the 

 thoracic ribs, though here, owing to the coalescence of the contiguous parts, there is no arterial 

 channel between the rib element and the true transverse process, which is represented by the 

 accessory processes (anapophyses), placed posteriorly at the root of the so-called transverse 

 process of human anatomy. Support is given to this view by the presence of a distinct costal 

 element in connexion with the transverse process of the first lumbar vertebra, which accounts 

 for the occasional formation of a supernumerary rib in this region. The cases of foramina in the 

 transverse processes of the lumbar vertebrae (see p. 275) are also noteworthy as supporting this view. 



In the sacrum the lateral part of the bone is made up of combined transverse and costal 

 elements, with only very exceptionally an intervening arterial channel. In the case of the 

 upper three sacral segments the costal elements are largely developed and assist in support- 

 ing the ilia, and they are called the true sacral vertebras ; whilst the lower sacral segments, 

 which are not in contact with the ilia, are referred to as the pseudo-sacral vertebrae. 



The anterior arch of the atlas vertebra is, according to Froriep, developed from a hypochordal 

 strip of cartilage (hypochordal spange). 



APPENDIX D. 

 MEASUREMENTS AND INDICES EMPLOYED IN PHYSICAL ANTHROPOLOGY. 



(1) Craniometry. 



The various groups of mankind display in their physical attributes certain features which are 

 more or less characteristic of the stock to which they belong. Craniology deals with these 

 differences so far as they affect the skull. The method whereby these differences are recorded 

 involves the accurate measurement of the skull in most of its details. Such procedure is included 

 under the term craniometry. Here only the outlines of the subject are briefly referred to ; 

 for such as desire fuller information on the subject, the works of Broca, Topinard, Flower, and 

 Turner may be consulted. 



The races of man display great variations in regard to the size of the skull. Apart altogether 

 from individual differences and the proportion of head -size to body-height, it may be generally 

 assumed that the size of the skull in the more highly civilised races is much in excess of that 

 displayed in lower types. The size of the head is intimately correlated with the develop- 

 ment of the brain. By measuring the capacity of that part of the skull occupied by the 

 encephalon, we are enabled to form some estimate of the size of the brain. The cranial capacity 

 is determined by filling the cranial cavity with some suitable material and then taking the 

 cubage of its contents. Various methods are employed, each of which has its advantage. The use 

 of fluids, which of course would be the most accurate, is rendered impracticable, without special 

 precautions, owing to the fact that the macerated skull is pierced by so many foramina. As a 

 matter of practice, it is found that leaden shot, glass beads, or seeds of various sorts are the most 

 serviceable. The results obtained display a considerable range of variation. For purposes of 

 classification and comparison, skulls are grouped according to their cranial capacity into the 

 following varieties : 



Micro-cephalic skulls are those with a capacity below 1350 c.c., and include such well-known 

 races as Andamanese, Veddahs, Australians, Bushmen, Tasmanians, etc. 



Mesocephalic skulls range from 1350 c.c. to 1450 c.c., and embrace examples of the following 

 varieties : American Indians, Chinese, some African Negroes. 



Megacephalic skulls are those with a capacity over 1450 c.c., and are most commonly met 

 with in the more highly civilised races : Mixed Europeans, Japanese, etc. 



Apart from its size, the form of the cranium has been regarded as an important factor in 

 the classification of skulls ; though whether these differences in shape have not been unduly 

 emphasised in the past is open to question. 



The relation of the breadth to the length of the skull is expressed by means of the cephalic 

 index which records the proportion of the maximum breadth to the maximum length of the 

 skull, assuming the latter equal 100, or 



Max. breadth x 100 _ 



TUT i ii. = Cephalic index. 



Max. length 



