BONNEMAISONIA. 



[ 94 ] 



BORACIC ACID. 



spending to the canaliculi (fig. 75). This is 

 best seen in sections of rachitic bones. 



The last and most curious part of the 

 process consists in portions of the bony 



Fig. 1^. 



Magnified 300 diameters. 



Bone-cells in progress of development, removed from 

 the same bone (fig. 75), still distinctly separate from the 

 intercellular substance, a, single bone-cells ; b, com- 

 pound cells corresponding to one primary and two se- 

 condary cells ; c, the same consisting of three cells. 



substance becoming absorbed, rendering it 

 at first spongy, and then giving rise to the 

 formation of large cavities, the cancelli. 



Abnormal or adventitious bone agrees in 

 general structure with the normal ; it is met 

 with in all stages of development. 



To examine the structure of bone, thin 

 sections are requisite. The method of making 

 these is described under Preparation. By 

 macerating bone in mm-iatic acid, diluted 

 withfromlO to 20 partsof water, the inorganic 

 matter is removed, the cartilage being left. 

 Thin sections of this can then be readily made. 



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, m hich 

 does not easily enter the canaliculi, yet 

 greatly increases the general transparency of 

 the section. 



BiBL. Kolliker, MikrosJc. Anat. ii.; Tomes, 

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

 Tissue; Quekett, Trans. Micros. Soc. 1846; 

 Paget, Report, Sfc, Brit, and For. Med. Rev. 

 1842. See Chemistry. 



BONNEMAISONIA, Ag.— A genus of 

 Laurenciaceae (Florideous Algae), bearing 

 pear-shaped spores in stalked ceramidia. 



B. asparagoides is a sea-weed with a frond 

 4 to 1 2 inches long, growing near low- water 

 mark or deeper, of delicate feathery character 

 and deep crimson colour. 



BiBL. Harvey, P/^yc. -BnV. pi. 51; Brit. 

 Marine Algae, p. 97. pi. 12 D ; Grevilie, Algce 

 Brit. 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 pm'ified 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 de- 

 posited from the hot aqueous solution are 

 mostly six-sided plates : they exhibit the 

 phaenomena of analytic crystals, but at their 

 lateral surfaces or edges only, and when their 

 entire surface appears dark or coloured with 

 the polarizer alone, the crj^stals are found to 

 be laminated. But when an alcoholic solu- 

 tion of boracic acid is evaporated on a slide, 

 or still better, when some phosphoric acid is 

 added to solution of borax, and the mixture 

 evaporated, minute disks or spherules of the 

 acid are formed; these, when carefully ex- 

 amined, 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 undistinguishable, and the circum- 

 ference of the disk appears entire ; in others, 

 the free extremities of the needles are seen 

 projecting beyond the circumference. They 

 are perfectly colourless, and almost transpa- 

 rent when viewed by ordinary light, immersed 

 in balsam. But when examined with polar- 

 ized light, each disk exhibits the most beau- 

 tiful cross and coloured rings, just as in the 

 case of the oxalurate of ammonia, in which 

 we have described the phaenomenon more 

 fully. 



In some of the specimens of boracic acid, 

 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 solution will sometimes yield them, at 

 others not. Drops of the solution should be 

 placed upon a number of slides, and these 

 laid upon a warm iron plate. The disks are 

 much more beautiful than those of oxalurate 



