380 



THE MICROSCOPE. 



their having been first described by our countryman Clopton Havers, 

 are termed to this day the Haversian canals, and serve for the trans- 

 mission of blood-vessels into the interior of the bone. Further than 

 this we cannot proceed without optical assistance ; but if now a thin 

 transverse section of the same bone be made, and be examined by the 

 microscope with a power of 200 linear, we shall see the Haversian 

 canals very plainly, and around them a series of concentric bony 

 laminae, from three to ten or twelve in number. If the section should 

 consist of the entire circle of the shaft, we shall notice, besides the 

 concentric laminae round the Haversian canals, two other series of 

 laminae, the one around the outer margin of the section, the other 

 round the inner or medullary cavity. Between the laminae is situated 

 a concentric arrangement of spider-like looking bodies, which have, by 

 different authors, received the name of osseous corpuscles, lacunae, or 

 bone-cells, according as to whether they were ascertained to be solid 

 or hollow : these bone-cells have little tubes or canals radiating from 



fig. 181. 



1. A horizontal section of the lower jaw-bone of a Conger eel, which exhibits a single 

 plane of bone-cells arranged in parallel lines. There are no Haversian canals pre- 

 sent ; and when this specimen is contrasted with that of fig. 180, No. 1, it will be 

 noticed that the canaliculi given off from each of the bone-cells of this fish are very 

 few in number in comparison with that of the reptile. 



2. A portion of the cranium of a Siren (Siren lacertina), which is remarkable for the 

 large size of the bone-cells and of the canaliculi, they being larger in this animal 

 than in any other yet examined. As in the preceding specimen, no Haversian 

 canals are present. 



them, which are termed canaliculi by some authors, and tubes and 

 pores by others : those bone-cells which are nearest the Haversian 

 canals have the canaliculi of that side radiating towards the opening 



