CHOLERA-FLY. 



CHORDA DORSALIS. 



CHOLERA-FLY. Knox, Lancet, 1853, 

 ii. 479. 



CHOLES'TERINE. This substance 

 exists naturally in most animal liquids in a 

 state of solution ; also in many animal solids, 

 as in the blood, the bile, the meconium, 

 the brain and spinal cord. As an abnormal 

 product, it occurs in the crystalline form in 

 the bile, biliary calculi, various dropsical 

 effusions, the contents of cysts, pus, old 

 tubercles, malignant tumours, the excre- 

 ments, expectoration of phthisis, &c. 



In the vegetable kingdom it occurs in 

 peas, beans, almonds, many seeds, &c. 



The crystals form thin pearly rhombic 

 plates (PI. 13. fig. 21). The acute angles 

 are =79 30', the obtuse =100 30'. Some- 

 times the angles are truncated. 



Cholesterine is insoluble in water and 

 solution of potash, even when boiling ; but 

 soluble in ether and boiling alcohol, crystal- 

 lizing on cooling. 



It is most easily procured from a gall- 

 stone by boiling in alcohol ; it falls on cool- 

 ing. The crystals thus obtained are usually 

 thicker than the natural plates. 



CHONDRACAN'THUS. A genus of 

 Crustacea, of the order Siphonostoma, and 

 family Lernasopoda. 



C. Zei. Found upon the gills of Zeus, 

 the Dory. Body is covered with short re- 

 flexed spines. Length 4-5". 



BIBL. Baird, Brit. Entomostr. 327 ; Me- 

 gnin, Parasites, 442. 

 ' CHONDRIA, As-. See LAUREXCIA. 



CHONDR1NE. The gelatinous matter 

 of the permanent true cartilages. 



Its solution differs from that of the gela- 

 tine of bones &c., in being precipitated by 

 acetic acid, acetate of lead, and alum. The 

 acetic precipitate is insoluble in excess. 



It is coloured red by Millon's test ; but is 

 unaffected by that of Pettenkofer. 



CHON'DRUS, L. A genus of Crypto- 

 nemiaceae (Florideous Algae), composed of 

 cartilaginous sea-weeds with flat dichoto- 

 mously-divided fronds, the cellular structure 

 of which exhibits three layers a central of 

 longitudinal filaments, an intermediate of 

 small roundish cells, and an outer of ver- 

 tical coloured and beaded rows of cells, 

 the whole imbedded in a tough <f inter- 

 cellular" matrix. See INTERCELLULAR 



SUBSTANCE. 



Fructification : spores contained in favel- 

 lidia immersed in the frond ; tetraspores 

 collected in imbedded sori ; and " nema- 

 thecia," 1 tubercles composed of radiating 



filaments (antheridia ?). C crispus becomes 

 horny when dry, and is the Irish moss or 

 Carrageen of the shops. 



BIBL. Harvey, Br. Mar. Alg. pi. 17 D ; 

 Phyc. Brit. pi. 63 & 187 ; Greville, Alg. 

 Brit. pi. 15. 



. CHOR'DA, Stackh. A genus of Larni- 

 nariaceae (Fucoid Algae), with fronds of 

 a peculiar, simple cylindrical form ; two 

 species, C.Jilum and C. lomentaria, are found 

 between tide-marks on British coasts ; the 

 former grows from 1 to 20 or even 40 feet 

 long, with a greatest diameter at half its 

 length, of 1-4 to 1-2". The cord-like frond 

 is tubular, but has at intervals thin dia- 

 phragms, formed by interwoven transparent 

 filaments. The wall of the tube is com- 

 posed of a number of layers of very regular 

 six-sided cells, upon which are implanted 

 little erect clavate cells which coat the 

 entire surface of the frond. These present 

 two forms, apparently constituting oospo- 

 ranges (spores, Harvey, paranemata, Ag.) 

 and trichosporanges, (antheridia, Harvey, 

 spores, Ag.). The first are single sacs pro- 

 ducing a number of zoospores; the second 

 are filaments composed of about five joints, 

 each of which gives birth to a zoospore. 



BIBL. Harvey, Br. Mar. Alg. 31, pi. 3 B; 

 Phyc. Brit. 107, &c. ; Thuret, Ann. Sc. Nat. 

 3 s^r. xiv. 240, pi. 29. figs. 5-10 ; Derbes 

 and Solier, Ann. Sc. Nat. 3 se*r. xiv. 268, 

 pi. 33, figs. 7-10 ; Kiitzing, Phyc. gen. pis. 

 28 & 29. 



CHORDA DORSA'- r - 12a 

 LIS, or NOTOCHORD. , 



The embryonic represen- . * 



tative of the spinal co- 

 lumn of the Vertebrata ; 

 the permanent spinal 

 column of the Cartilagi- 

 nous Fishes. It some- 

 times forms a spindle- 

 shaped, transparent, gela- 

 tinous-looking cord, with 

 the broadest part near 

 the tail; at others it is 

 cylindrical or conical, 

 rounded anteriorly and 

 tapering posteriorly. 



It usually consists of 

 an outer comparatively 

 thick and firm structure- 

 less membrane, forming of ^ sheep! rathermore 



a sheath, and of pale nu- than 1-2" in length, o, 

 cleated cells, which fill sheath; b, cells. 

 the sheath (fig. 126). In 

 some instances, however, its structure is 



Magnified 350 diam. 

 Portion of the chorda 



