300 SPECIAL HISTOLOGY. 



bone is burnt and the fragments crushed, it affords, according 

 to Tomes, minute angular granules, from ith to ^th the diameter 

 of the humau blood corpuscle, and measuring, according to 

 Todd and Bowman, ^th — i^th of an inch, and which are 

 also rendered evident when bone is boiled in a Papins' diges- 

 ter. From these particulars, and from the granular aspect of 

 fresh bone, which has also been noticed by Tomes and by 

 Todd and Bowman, and moreover from the pretty nearly equal 

 size of the granules visible in it, with those described by Tomes, 

 and lastly, from the circumstance that bone treated with 

 hydrochloric acid, as well as when calcined, both present a 

 perfectly homogeneous substance without vacuities, it may be 

 assumed that the osseous tissue consists of an intimate mixture 

 of inorganic and organic compounds, in the form of closely 

 connected minute granules. 



§ 91. 



Bone Cavities or Cells, and Canaliculi, {lacunae et canaliculi 

 ossium.) — In dried sections of bone, there are visible, scattered 

 throughout the entire osseous substance, in all the lamellse, 

 microscopic melon-seed shaped corpuscles, with numerous, fine, 

 ramified, and partially anastomosing rays, whose opaque and 

 white colour (as viewed by direct light) is due, not to the 

 deposition of calcareous salts, as was formerly supposed, and on 



found in the skeletons of the lower vertebrata, we have bone tissue without obvious 

 granularity, and without obvious structure ; and although it forms but a small part of 

 the general mass, yet from its constant presence at all ages and in all subjects, it 

 must he regarded as an integral and normal part of mammalian bone. The granular 

 condition of bone tissue is tolerably obvious in all preparations, though it is much 

 more marked in some specimens than in others. The amount of the component 

 granules varies in different parts of the same specimen, and in specimens taken from 

 different parts of the skeleton. Thus, in one situation, we may see laminae with a 

 highly transparent part gradually merging into a transparent tissue, while in another 

 the laminae may he granular throughout. Again, in youug bone developed in carti- 

 lage, the part between the cells becomes highly granular, fragments of which may 

 be found in certain adult bones, as in the petrous portion of the temporal bone. 

 Bone near the articular surface frequently presents a well-marked granularity.'' 



We may remark, in addition to this very just account of the minute structure of 

 bone, that, of the lower vertebrata above referred to, the Skate offers one of the best 

 examples of structureless bone, in those polygonal plates which are developed (not 

 on the surface, as is commonly said, but) in the inferior of the cartilaginous skeleton. 

 —Eds.] 



