15 



another; and these again, of fibres running length, 

 ways ; some to the extremity of the bone, some not so 

 far. Yet none of them terminate there ; but are coo- 

 tinuetl transversely, and as it were arched, the fibres of 

 one side meeting and uniting with those of the other, 

 and this at each extremity. 



These plates are differently disposed in different 

 bones : in those that have a large cavity, they are 

 contiguous on each side, and very closely united. In 

 those whose cavities are small,many of the inner plates 

 are distant from each other ; having little long celts 

 between them. In bones whose plates are contiguous, 

 there are pores through and between them, (beside 

 those for the blood-vessels.) The first pierce them 

 transversely, from the cavity to the external surface 

 of each plate. The second run lengthways between 

 the plates, and diffuse an oil with which they are sup- 

 plied by the transverse pores. 



The bones are generally bigger at each end than 

 in the middle, that the joints may be firm, and the 

 bones not so easily dilocated. But to strengthen the 

 middle of the bone, the fibres there are more closely 

 compacted. Likewise the bone, being large and hol- 

 low, is not so eir ; Jy broke as if it had been solid and 

 smaller ; for of two bones of equal length and equal 

 number of fibres, that is stronger which has the larger 

 diameter. 



The blood. vessels usually enter the ends of the 

 bones ; the arteries at one end, the veins at the other. 

 The medullary vessels commonly enter the sides of the 

 bone, and that obliquely. 



The marrow is covered with a membrane, wherein 

 are inclosed little ba^s. In these bags are glandulous 

 bladders, serving both to secern the marrow from the 

 blood, and to receive it. Both these and the bags 

 have passages into each other, whereby the marrow 

 has free course. It passes first through the transverse 

 pores of the first internal plate into the longitudinal 

 ones. Thence it proceeds into other transverse pores, 

 when it alters its course again, and exudes farther. 



