386 SPECIAL HISTOLOGY. 



so that the latter in great part, and also the former, are very 

 frequently rendered invisible ; the same thing happens in 

 water and thicker turpentine, though less rapidly, whence, 

 before these agents have produced their effect throughout, many 

 of the lacunae and canaliculi are beautifully shown. If it be 

 desired to preserve the lacuna? and canaliculi permanently 

 visible, it is best to polish a thin section, by rubbing it between 

 two glass plates. It may then be examined without the 

 addition of fluid, and presents as perfect figures as those repre- 

 sented in figs, 115 — 117. The grinding of the bone with oil 

 is not to be recommended, because the lacuna? then become 

 filled with the oil, and even after thorough treatment with 

 ether can seldom be rendered distinct. !Next to sections of 

 bone, the investigation of the bone-cartilage is the most worth 

 while. This tissue is prepared by the treating of bone in the 

 cold, with diluted hydrochloric acid (1 part acid, 10 — 20 water), 

 until the fluid, which is to be frequently changed, no longer 

 affords any precipitate with ammonia ; for which purpose, in 

 small fragments of bone, some hours, in entire bones several 

 days, are required. From the cartilage thus obtained, sections 

 are now to be made with a sharp knife in all directions, 

 suitable chiefly for the study of the Haversian canals and 

 lamella?, which may even be raised from the surface. The 

 lacuna?, also, are still visible ; their prolongations or canaliculi 

 appear as fine streaks, and their nuclei are seen without fur- 

 ther trouble, especially also after treatment with potass, or in 

 cartilage which has been half dissolved by boiling in water. 

 After longer maceration in hydrochloric acid, the lacuna? even 

 become isolated, as stellate bodies with delicate walls, or, in 

 the cementum of the horse's tooth, as structures corresponding 

 to the former cartilage-cells. After long softening of bone- 

 cartilage in water, the lamellar systems of the Haversian 

 canals become more or less completely separated, presenting 

 the appearance of short, coarse fibres among the larger lamella? 

 (Gagliardi's claviculi). If bone be exposed in a platinum 

 capsule to a strong white heat, the organic parts burn away, 

 the bone becoming at first black, and ultimately perfectly white; 

 and if due care be taken, the earthy constituents are left, 

 completely retaining the original figure of the bone. Pre- 

 parations of this kind are proper for the study of the laminated 



