( 130 ) 

 tragment, to the naked eye, appeared no larger than the fpot, 

 fig. 15. E FG is the point of a Imall needle to which this frag- 

 ment of Bone was fixed. 



The firll and fmallcll fort of the tubes I have been defcribing I 

 could not obferve in this fragment ; becaufe, when the Bone is 

 thus cut, the fmall tubes appear lying together in a confufed man- 

 ner, like u-regular globules ; the fecond fort of tubes I have repre- 

 fentedin the figure, and thefe often appear like dark fpots, becaufe 

 their orifices are ftoppcd up in cutting the Bone, and are more dif- 

 ficultly diliinguilhcd when the knife does not divide them accurately 

 by a tranfverfe feclion ; for if the fedion is ever fo little oblique, 

 it is impolfible to difcover them. This fecond fort of tubes are 

 reprefented at letters H H H. 



The third fort of tubes I have reprefented at III: this third 

 fort I have not only feen adjoining each other in circular order,, 

 but alfo in a different order, in like manner as the large veflels in 

 wood. 



The fourth fort of tubes, which are very large in comparifon 

 with the former ones, is pointed out by the letters KK. The 

 curved line L, and that at M, are cracks in the Bone, made by the 

 edge of the knife, which often happens, efpecially when the knife 

 is not ftiarp enough. 



Befides the four forts of tubes before mentioned, forming length- 

 ways the fubftance of the Bone, I often imagined I faw fome tubes 

 taking a contrary courfe, and which feemed to me to proceed from 

 the internal part, and terminate at the furface of the Bone; and 

 I alfo thought that thefe were of two fizes, the leaft which I alfo 

 imagined, were analogous to the fmallell of thofe tubes which lay 

 lengthways in the Bone. 



The rcafon why I could not truly perceive the tubes proceeding 

 from the cavity to the circumference of the Bone was, I think, 

 this, that thefe tubes were far dillant from each other; and, indeed, 

 I thought that one tube lay among the longitudinal ones, as if au 



