14 OSSEOUS TISSUE. 



and Bowman, and afterwards more fully by Kolliker, was one into 

 which it was the more easy to fall, because, on the one hand, these 

 air-containing spaces refract the light in its passage from the 

 osseous matrix into these cavities in such a manner that these parts 

 appear perfectly dark in consequence of the deviation of the rays, 

 and thus resemble opaque objects, such as we often find (in another 

 form) in morbid concretions, and because, on the other side, it is 

 only with difficulty and by a very slow process that these empty 

 spaces and passages can be filled with fluids. (The best fluids for 

 this purpose are the oils arid balsams.) 



Virchow and Donders, and more recently Hoppe,* have shown 

 the extreme probability that these bone-corpuscles and their pro- 

 longations are not simple excavations in the bone, but that they are 

 lined by a membrane, by finding that after the prolonged ebul- 

 lition of pieces of bone (the tegumentary bones of the sturgeon) the 

 corpuscles, with their prolongations, remained perfectly intact after 

 the solution of the matrix. Drummondf maintains, as Kolliker 

 had previously done, that a nucleus is constantly present in the 

 bone-corpuscles. 



The easiest method of demonstrating that the bone-corpuscles 

 and their prolongations are cavities, is to apply a little pure turpen- 

 tine or Canada balsam to the edge of a long thin slip of bone 

 (which, after perfect drying, serves the best to exhibit these parts) 

 and to examine it under the microscope ; we then perceive the 

 dark bone-corpuscles and their prolongations very gradually become 

 light, by slowly absorbing the turpentine, and thus losing their 

 strong refractive power. 



These minutest cavities or pores do not contain air in the 

 fresh moist substance; they must be filled with a fluid whose 

 refracting power is not very different from that of the matrix of 

 bone, as is obvious from the investigation of fresh or thoroughly 

 moistened osseous tissue ; hence a deposition of calcareous salts 

 within them is out of the question. No examination has as yet 

 been made of the contents of these pores and cavities in fresh 

 bones ; it must, however, suggest itself to every one, that this 

 system of most minute cavities which communicates on all sides 

 with the Haversian canals (the vascular cavities of the bones) must 

 take up the transudations from the vessels (the nutrient fluid) and 

 reconvey the effete particles in a state of solution into the Haver- 



* Arcli. f. pathol. Anat. Bd. 5, S. 176. 



t Monthly Journ. of Aled. Science. Vol. 14, p. 285. 



