268 report— 1846. 



belong. The homologous haemal arch exists in the same free and detached 

 condition in cetaceans and enaliosaurs ; but in all other air-breathing verte- 

 brates it is connected with the iliac bones and completes the typical character 

 of the proper sacral vertebra. The bony haemapophyses of the lumbar vertebrae 

 are found suspended in the fleshy abdominal walls of certain saurians : but in 

 the region of the thorax in these and higher vertebrates, the haemapophysis 

 (fig 15, h) articulates by one end to the pleurapophysis {pi) and by the 

 other to the haemal spine (sternal bone, hs) ; or its lower end is attached to a 

 contiguous haemapophysis ; or it is suspended freely from the pleurapophyses 

 (as in the ' floating ribs ' of man and mammals), or it may be joined below 

 to the sternum, and have its upper end free, as in the seventh dorsal vertebra 

 of the Ciconia Argala. When the upper end of the haemapophysis articulates 

 with the pleurapophysis in birds, it is usually by a distinct condyloid joint, 

 with smooth articular cartilage and a synovial capsule. 



Where haemapophyses exist in the tail, they articulate directly to the 

 under part of the centrum, or to two centrums at the intervertebral space ; 

 and are either free at the opposite end, as in some caudal vertebrae of ser- 

 pents and in those of the enaliosaurs, or they are confluent with each other 

 at their distal ends ; when each pair of haemapophyses forms the so-called 

 V-shaped or chevron-bone. The changes of position of that detached ' pubic 

 arch ' or ' chevron-bone ' which supports the ventral fins in fishes aflbrded 

 Linnaeus the characters of the orders ' Abdominales,' ' Thoracici,' and 

 'Jugulares' in the ' Systema Naturae'; and its immortal author, in giving the 

 name ' Apodes ' to those fishes in which the ventral fins were absent, con- 

 cisely indicates his perception of their relation to the hind-legs of batrachia 

 and the lower limbs of man. If, then, mere change of relative position, 

 however extensive, failed to conceal the special homology of the detached por- 

 tion of the pelvic arch and its appendages from the keen-sighted naturalist, 

 still less ought such a character to blind the philosophic anatomist to the 

 general homology of such detached vertebral elements, or prevent his tracing 

 them, wherever he may find them, to the remainder of their proper segment; 

 especially when its place is so clearly and beautifully indicated, as it is by the 

 condition of the pelvic arch in the perennibranchiate reptiles (fig. 28). 



The function of the haemapophyses is to complete, with or without a haemal 

 spine, the haemal arch of the vertebral segment ; and, in so far to protect the 

 haemal or visceral cavities and support their contents. They give attachment 

 to the lower or ventral portions of the primary muscular segments 'myo- 

 commata'*, called ' intercostals' in the thorax, and 'recti abdominis' in the 

 abdomen of the higher vertebrata ; and they thus serve as fulcra to the 

 muscles that expand and contract the abdominal or thoracic-abdominal cavity : 

 and sometimes more directly aid in these movements by the elasticity resulting 

 from an arrest in their histological development at the cartilaginous stage, e.g. 

 in the thorax of most mammals. Haemapophyses may support or aid in sup- 

 porting diverging appendages ; and in giving attachment to the muscles of 

 those appendages. The haemapophyses are usually slender, longer, or shorter 

 simple bones; but are broad and flat, overlapping each other in the thorax 

 of monotremes : they become broader and shorter in the expanded and fixed 

 thoracic abdominal bony case of chelonians, and are still broader where they 

 close the pelvic arch in the plesiosaurs. In the abdominal region of these ex- 

 tinct saurians and in crocodiles, the freely suspended haemapophyses are com- 

 pounded of two or more overlapping bony pieces. 



* See the description of these segments, usually confounded under the name of the ' great 

 lateral muscle ' or ' longitudinal muscles ' in fishes. — Hunterian Lectures on Vertebrata, 8vo, 

 pp. 163-165. 



