262 report — 1846. 



side of the centrum or the base of the neural arch, called ' diapophysis,' a di- 

 stinct part from the autogenous parapophyses in fishes. The anterior verte- 

 brae of crocodiles have an exogenous inferior transverse process from the side 

 of the centrum, answering to the 'parapophysis,' as well as an upper transverse 

 process or ' diapophysis ' developed from the base of the neurapophysis : and 

 the proximal end of the pleurapophysis bifurcates and articulates with both 

 transverse processes, circumscribing with them a foramen at the side of the 

 centrum. The same structure obtains in the cervical and anterior thoracic 

 vertebrae of birds and mammals : thus the rib (pi) in fig. 15 articulates to the 

 parapophysis p and the diapophysis d. Very few, however, of the thoracic 

 ribs in the cetaceans offer this structure ; the first or second may reach the 

 centrum, but the rest are appended to the ends of the long diapophyses, and 

 a character of affinity to the saurians is thus manifested. The cervical re- 

 gion is distinguished by the brevity of the pleurapophyses and the absence 

 of bony haemapophyses, in saurians, birds, and mammals ; but in the warm- 

 blooded classes the short floating vertebral ribs soon anchylose to the diapo- 

 physes and parapophyses, and constitute thereby the ' anterior roots of the 

 perforated transverse process ' of anthropotomy*. The cervical pleurapo- 

 physes are indicated diagrammatically at pi, in the neck of the embryo skele- 

 ton (fig. 25): those of the seventh cervical vertebrae sometimes attain in 

 the human subject proportions which acquire for them the name of ' ribs.' 

 The pleurapophyses retain their moveable articulation in the ninth, and 

 sometimes the eighth, vertebrae of the elongated neck of the three-toed 

 sloths f. 



The thoracic or dorsal vertebrae of mammalia are characterized by the free ar- 

 ticulations of the pleurapophyses (fig. 25, pi) : most of these are much-elon- 

 gated, and most, if not all, support haemapophyses (ib. h) ; which, in a greater 

 or less number of the anterior vertebrae, articulate with haemal spines (ib. hs), 

 completing the arch : these spines commonly remain distinct, and are called, 

 some ' sternebers,' others ' manubrium,' and ' xiphoid appendage,' and to- 

 gether they constitute the ' sternum.' In most mammals the thoracic hasma- 

 pophyses are cartilaginous : they become ossified in Dasypus, Myrmecophaga, 

 the megatherioids and monotremes. The hinder pleurapophyses, which pro- 

 gressively diminish in length, also, usually become simply suspended to the 

 diapophyses: all the ribs are so attached in Balcena longimana, according 

 to Rudolphi. The lumbar vertebrae, which in some mammals show, in the 

 foetal state, distinct rudiments of pleurapophyses more minute than those 

 in the neck, have them soon anchylosed to the extremities of the diapo- 

 physes, which are thus elongated; and the vertebra is characterized in anthro- 

 potomy' as ' having no ribs, but simple imperforate transverse processes.' The 

 haamapophyses of these segments of the skeleton are represented by the 

 ' inscriptiones tendineae' (fig. 25, h") ; they do not advance even to the state 

 of cartilage, but retain the primitive condition which they presented in the 

 corresponding part of the trunk in fishes. 



If a vertebra succeeding the lumbar or abdominal ones have its haemal 

 arch completed, as in the thorax, by pleurapophyses and haemapophyses, 

 with diverging appendages, forming the ' pelvic arch and hind or lower 

 limbs,' it is called a ' sacrum ' (fig. 28, d', h, a). If two or more vertebrae 

 anchylose together, without such completion of the typical character, they 

 likewise are said to form a ' sacrum,' of which an example may be found in 



* Meckel, Archivfiir Physiologie, B. i. (1815) p. 594, pi. vi. fig. 12, e ; and System der Ver- 

 gleichend. Anatomie, B. ii. p. 294. 



t Prof. Th. Bell, Trans. Zool. Society, i. p. 115. pi. 116, a, b. 



