108 



M A M M A L I A. 



number of transverse and oblique processes as the 

 last five of the neck ; but those of the back have long 

 pointed spinous processes, and those of the lower 

 nave processes of the same kind, but shorter and 

 blunted. The spinous processes give the spine a firm 

 embedment in the muscles ; the lateral ones have 

 the ribs soldered to their inner surfaces, with the 

 head of the rib resting on the thick or articulated 

 part of the vertebra ; and the oblique processes are 

 the principal means by which dislocation is pre- 

 vented. In proportion as the column has more weight 

 to carry, and is less supported by the muscles and 

 ribs, its diameter, and also the articulating surfaces 

 of the vertebrae are enlarged. All these have the 

 cavity for the spinal marrow ; but they have no 

 lateral holes. 



The sacrum, which is again deeply imbedded in 

 muscles, has three spinous processes, but no oblique 

 ones ; within it the spinal marrow terminates in a tri- 

 angular cavity. It affords support to the spine ; and 

 it is also the centre of the bones of the pelvis. The 

 coccyx is a simple bone attached to the termination 

 of the sacrum, having no spine or internal cavity ; and 

 its chief purpose is to afford support to the terminal 

 part of the intestinal canal. 



The bones of the pelvis we have already men- 

 tioned. They are connected with the sacrum at 

 those portions which are called the haunch bones 

 (ilii) ; on the sides are the hip bones ; and the share 

 bones advance in front completing the cavity. The 

 haunch bones have two tuberous spines, and the share 

 bones or bones of the pubis, form an arch ; and in 

 the hip bones on each side there is situated the 

 cavity (acetabulum), which receives the condyle or 

 head of the femur or thigh-bone, which is the prin- 

 cipal articulation of the leg. These bones altogether 

 support the lower parts of the viscera, and also the 

 base of the spinal column ; but from the intervention 

 of two unions of separate bones on each side, between 

 the insertion of the femur and the spinal column, any 

 shock or concussion which is communicated to the 

 hip-bone by rapid motion of the legs, is not propa- 

 gated so as to jolt the contents of the spine, or to 

 disturb the viscera contained in the pelvis. The form 

 of the bones of the pelvis throws the articulations of 

 the femoral bone proportionally farther apart from 

 each other in man than they are in the other mam- 

 malia. In the male subject this distance may be con- 

 sidered as the one which conduces most to give the 

 trunk a stable base. Physiological causes render it 

 necessary that this measure should be rather exceeded 

 in the female ; and this is compensated by a slight 

 inclination to each other of the thigh-bones at their 

 distal, or knee ends, which gives a peculiarity to the 

 walk of females different from that of males. 



The remaining bones of the trunk are the sternum 

 and ribs. The sternum, or breast-bone, is flattened ; 

 and though they are intimately connected, it consists 

 of three bones, by which means its flexibility is much 

 increased, and the danger of fracture diminished. At 

 the under end it terminates, or is sheathed by the 

 cnsiform, or sword-shaped cartilage, which answers 

 in flexibility to the false ribs which form the lateral 

 walls of the lower part of the chest ; and their ster- 

 nal extremities are united by the cartilage. The 

 sternum contains cavities to which the ribs are arti- 

 culated ; but, as we have already mentioned, their 

 opposite extremities are merely soldered to the lateral 

 processes of the vertebrae, so that though the sternum 



and ribs are much more flexible than any other of 

 the assemblages of bone, and therefore a strain or 

 thrust is much less readily propasrated through them 

 to their union with the spine ; vet provision is made 

 against the possibility of jarring the spine even in 

 this way. We cannot, indeed, whatever part of the 

 skeleton we advert to, avoid noticing the universal 

 and admirable provision which is made for preserving 

 this organ from the effects of any of those violent 

 actions to which the other and less essentially vital 

 parts are necessarily often subjected in the exercise 

 of the body. There is no bone articulated directly 

 upon any part of the spine, but the unions are formed 

 by flexible matter, consisting partly of cartilage and 

 partly of elastic ligament ; and thus the brain and its 

 continuation are everywhere supported upon springs, 

 springs of a far more delicate nature than those which 

 we construct in our mechanics. When the pressure 

 is great upon the spring, that spring is doubled ; and 

 on the other hand, when the motion of the bone 

 approaching the spine is extensive and varied, as it is 

 in the blade-bone, there is an embedment of muscles 

 and of cellular membrane between the moving bone 

 and even the ribs. 



The seven true ribs on each side, extend from the 

 dorsal vertebrae to the sternum, having heads and 

 tuberous processes at their dorsal extremity, being 

 united to the sternum in front, and each being fur- 

 nished with a groove, along which an artery is con- 

 ducted. The five false ribs are connected to the 

 transverse processes of the lumbar vertebrae ; but at 

 their anterior extremities they are united by cartilage 

 one with another ; and the first one with the last ol 

 the true ribs. As this cavity of the body contains th<] 

 most active portion of the respiratory and circulating 

 systems, it is necessary that it should have the powei 

 of contracting and enlarging with very little effort ; 

 so that the pressure upon all the delicate organs and 

 vessels which it contains may be uniform ; and yel 

 that the requisite quantity of air in breathing should 

 be alternately received into the lungs and discharged 

 from them. Nothing can be more yielding to internal 

 pressure ; nothing better adapted for resuming its 

 shape when that pressure is removed ; and nothing 

 equally light in its structure can be stronger 01 

 more secure against external injuries than the chest. 



Bones of the arms. In considering these, the firsl 

 thing to be attended to is the point of insertion ; 

 because that, in a great measure, determines the 

 principal action of the articulated members. The 

 blade-bone and the clavicle are the two supporting 

 bones in the human subject. The blade- bone, as 

 already mentioned, is embedded in the muscles ol 

 the shoulder, and it is itself the point of insertion, 01 

 rather the surface of attachment. It is formed with 

 three ribs, a dorsal spine, and three processes, against 

 one of which the clavicle or collar-bone abuts ; and 

 the others support the muscles and prevent disloca- 

 tion of the shoulder joint. The glenoid cavity intc 

 which the condyle, or head of the humerus, is articu- 

 lated, is placed below one of those processes ; and 

 the lever of the bone, against which the collar-bone 

 acts, is placed a little further from the body than this 

 cavity. By this structure, the severest strain ir 

 pulling, pushing, or otherwise moving the extended 

 arm, is thrown upon the blade-bone, though the pecu 

 liar curve of the collar-bone, and that of the process te 

 which it is attached, enables it to give a firm support 

 and yet one which admits of considerable motion. 



