WITH THE MICROSCOPF. 121 



cellular substance of cartilage, and of its relation to the so-called 

 cells ; with observations upon the process of ossification." (Micro- 

 scopical Journal, 1863.) 



2is. Bone. Sections of bone are obtained in the manner alluded 

 to in p. 82. It is desirable to make sections of the whole extent of the 

 compact tissue. The observer will notice in thin sections, even of 

 young bones, spaces of very different sizes, resulting from the division 

 of a number of tubes (Haversian canals) in which the vessels, which 

 are distributed to the compact tissue, run. Now it appears from the 

 beautiful researches of Tomes and De Morgan, that this solid, hard, 

 compact tissue is perpetually undergoing removal and repair. An 

 Haversian canal increases in diameter by the gradual absorption of 

 the concentric lamellae of bone which surround it, and after a time, 

 a large space is formed (Haversian 'space). When this space has 

 reached a certain size, new bone is deposited, commencing at the 

 circumference and gradually proceeding towards the centre, until the 

 space has regained its small size and is again converted into a narrow 

 canal. The interstitial lamince upon this view are very readily 

 accounted for. They are, doubtless, the remains of old Haversian 

 systems only partially absorbed. (Phil. Trans., 1853). 



The growth of bone is investigated in young animals by mixing 

 madder with their food. In a very short time (even a few days) the 

 madder, which has an affinity for phosphate of lime, is deposited in 

 those parts of the bone nearest to the vascular surface. Young pigs 

 are the best animals for experiments of this kind. 



The arrangement of the vessels may be investigated in the bones 

 of an animal which has been injected with Prussian blue fluid. It is 

 well to add an excess of hydrochloric acid to the solution. After 

 the injection is complete, the bone may be soaked in dilute hydro- 

 chloric acid (one of acid to five of water), to dissolve out the earthy 

 matter, when the soft tissue which remains can be readily cut into 

 thin sections in various directions with a thin sharp knife. 



Not unfrequently the vessels of bone are found distended with 

 blood, thus producing a natural injection. It is difficult to cut and 

 grind the section thin enough for examination without altering the 

 masses of dried blood, but with care this may be effected. My 

 friend Mr. White has given me some beautiful sections of the antler 

 of the stag, in which all the vessels of the Haversian canals still 

 retain blood. 



Sections of bone may be preserved dry, in aqueous fluids, or in 

 Canada balsam. The dark appearance of the lacunae in sections of 

 dried bone is entirely due to their containing air. Their apparent 

 solidity led Purkinje, their discoverer, to call them bone corpuscles. 



