486 PHILOSOPHICAL TRANSACTIONS. [aNNO 1720. 



and dispersed themselves again. It is difficult to determine whether these 

 vessels bring any liquor into the bone, or carry it out ; but I rather think for 

 the latter purpose. 



Having placed another piece of bone before the microscope, with the 

 periosteum adhering to it, I could discover a great number of vessels, cut 

 through lengthwise, as they ran along the periosteum, and others cut through 

 transversely, and appeared as so many points, as is represented in fig. 4, by 

 KLOPftNA, where the bony part is marked klmna, in which, though no pores 

 or vessels are here represented, yet it is full of openings. That part repre- 

 sented by LOPftNM, we must not take to be entirely membranous ; for I am of 

 opinion, that that part of it lying next the bone, and which is represented by 

 LMN, is of a bony substance. 



I had another small piece of bone lying before a microscope, of which I 

 caused a part to be represented by rswxtv, fig. 5, in which rstv is the bone, 

 and swxt the periosteum, which in this place was no thicker than a thick hair 

 of a man's beard, but in another part of the same bone at a small distance, it 

 was full 4 times that thickness. 



I placed another piece of bone before a microscope in such a manner, that 

 the bone did not appear, but only the periosteum and the muscular fibres, which 

 were cut through transversely, and appeared to be surrounded by the fibrillae of 

 the periosteum, as is represented by yzcdab, fig. 6, where yzab is the perio- 

 steum, and zcDA are the fleshy fibres cut through transversely. This piece of 

 bone was taken from one of the ribs of a fat ox, and I was surprised to find, 

 that in this place, as 1 cut longwise through the rib, I could not discover any 

 particles of the marrow, whereas in other parts the rib abounded with them. 



Notwithstanding the great number of observations I have made on the bones, 

 and the membrane that surrounds them, commonly called the periosteum, I 

 have never been able to satisfy myself entirely about them. I still imagined, 

 that the part of the periosteum which immediately covers the bone, and is 

 strictly united to it, must have a degree of hardness approaching to that of the 

 bone, and that at a small distance from the bone, the periosteum must have a 

 softness and flexibility like that of the carneous and adipose membranes. 



I had kept 4 pieces of ribs of an ox, full 1 months, which were now grown 

 very dry. From one of these I tore off the periosteum, which I found stuck 

 much harder to the bone than I could have imagined, and I observed, that a 

 great many particles of this membrane were left on adhering to the bone. I did 

 this with design to make some observations on the superficial part of the bone, 

 which is not near so hard as those bony particles that lie a little deeper. From 

 this bone I cut off some very thin slices, both lengthwise and transversely, one 



