BONE. 



[ 113 ] 



BORACIC ACID. 



walls of the cancelli and canals, of genera- 

 tions of stellate connective tissue corpus- 

 cles (osteoblasts), forming a pseudo-carti- 

 lage, occurs, which becomes calcined to form 

 the true bone; the absorption of the calci- 

 fied cartilage, and the deposition in its place 

 of the new tissue, continuing until the 

 structure of the bone is perfected. 



But in certain bones, as the flat skull- 

 bones, the jaw-bones &c., the bone is formed 

 without the aid of cartilage. Here the in- 

 ner surfaces of the periosteum produce the 

 osteoblasts, which ultimately become the 

 bone-corpuscles. 



In certain morbid conditions, as in rickets, 

 the development of the bone is arrested at 

 the state of ossified cartilage ; secondary 

 deposit occurring in the cells of the primary 

 cartilage as in the case of vegetable cells 

 (tig. 74), the spaces left having great 

 resemblance to the lacunae and canaliculi of 

 bone. 



Adventitious bone agrees in general struc- 

 ture with the normal ; and is met with in 

 all stages of development. 



To examine the structure of bone, thin 

 sections are requisite. The method of ma- 

 king these is described under PREPARATION. 

 By macerating bone in muriatic acid dilu- 

 ted with from 10 to 20 parts of water, or 

 nitro -chromic acid, the inorganic matter is 

 removed, the cartilage being left. Thin 

 sections of this can theii be readily made, 

 and stained with picro-carrniue or purpu- 

 rine. 



The canaliculi are not easily seen when 

 sections of bone are immersed in liquids ; 

 for these fill them up. But it is a difficult 

 matter to measure the lacunae, unless the 

 section be moistened with turpentine or 

 other liquid. 



Very thin sections may be preserved in 

 the dry state ; those which are thick may 

 be mounted in inspissated Canada balsam, 

 which does not easily enter the canaliculi, 

 yet greatly increases the general trans- 

 parency of the section. 



BIBL. Kolliker, Mikr. Anat. ii. ; Tomes, 

 Todd's Cyd. Anat and Phys., art. Osseous 

 Tissue; Quekett, Tr. Mic. Soc. 1846; 

 Quain and Sharpey, Anat. ; H. Miiller, 

 Sieb. # Kott. Zeitschr. ix. 147; Rutherford, 

 Hist. 82 ; Schoney, Sch. Arch. xii. devel. 

 (M. M. Jn. xvi. 1876, 67, figs.); Frey, 

 Histoloqie, and the full BIBL. therein. 



BONNEMAISO'NIA, Ag. A genus of 

 Laurenciaceae (Florideous Algae), bearing 

 pear-shaped spores in stalked ceramidia. 



B. asparagoides (PI. 4. fig. 15) has a frond 

 4 to 12 inches long, growing near low-water 

 mark or deeper, of delicate feathery character 

 and deep crimson colour. 



BIBL. Harvey, Phyc. Brit. pi. 61; Br. 

 Mar. Algce, p. 97, pi. 12 D ; Greville, Alyce 

 Br. p. 106, pi. 13. 



BORACIC ACID is the acid of the 

 well-known salt, borax, in which it exists 

 combined with soda, in the proportion of two 

 atoms of the acid to one of the base. Boracic 

 acid is prepared by mixing three parts of 

 borax dissolved in twelve parts of boiling 

 water with one part of sulphuric acid or 

 common oil of vitriol. As the mixture cools, 

 the boracic acid separates in the crystalline 

 form. It may be purified by re-solution in 

 hot water, and subsequent cooling ; finally, 

 the crystals are pressed between blotting- 

 paper, and dried. Boracic acid belongs to 

 the doubly oblique prismatic system ; and 

 the crystals possess two optic axes. Those 

 deposited from the hot aqueous solution are 

 mostly six-sided plates ; they exhibit the 

 phenomena of analytic crystals, but at their 

 lateral surfaces or edges only ; and when 

 their entire surface appears dark or co- 

 loured with the polarizer alone, the crystals 

 are found to be laminated. But when an 

 alcoholic solution of boracic acid is evapo- 

 rated on a slide, or, still better, when some 

 phosphoric acid is added to a solution of 

 borax, and the mixture evaporated, minute 

 disks or spherules of the acid are formed ; 

 these when carefully examined, are seen 

 to be composed of minute needles radiating 

 from a centre, exactly as in the oxalurate 

 of ammonia. In some of them the needles 

 are so closely in contact that they are un- 

 distinguishable and the circumference of 

 the disk appears entire ; in others, the free 

 extremities of the needles are seen projecting 

 beyond the circumference. They are per- 

 fectly colourless, and almost transparent 

 when viewed by ordinary light, immersed in 

 balsam. But when examined with polarized 

 light, each disk exhibits the most beautiful 

 cross and coloured rings, just as in the case 

 of the oxalurate of ammonia, in which we 

 have described the phenomenon more fully. 



In some of the specimens of boracic a.cid 

 the crystals form elegant arborizations, 

 which also possess considerable analytic 

 power. 



The proportions of phosphoric acid and 

 borax requisite to produce the disks cannot 

 be laid down : they can only be prepared by 

 accident in a number of trials. Even the same 



