C HOLER A-FLY. 



[ in ] 



CHORDA DORSALIS. 



CriOLERA-FLY.— Knox, Lancet, 1853, 

 ii. 471). 



CllOLES'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 crystalliuo form in 

 the bile, biliary calculi, various dropsical 

 effusions, the contents of cysts, pus, old 

 tnbercles, 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 vi^ien 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. 



CHONDRACAX'THUS.— A genus of 

 Crustacea, of the order Siphonostoma, and 

 family Lernaeopoda. 



C. Zei. Found upon the giUs of Zeus, 

 the Dory. Body is covered with short re- 

 flexed spines. Length 4-5". 



BiBL. Baird, Brit. JEntomostr. 327 ; Me- 

 gnin. Parasites, 442. 



CHONDRIA, Ag. See Latteencia. 



CHONDRINE.— 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 MiUon's test ; but is 

 imaffected by th at of Pettenkofer. 



CHOX'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 " inter- 

 cellular " matrix. See Intercbllulae, 



SUP.STAXCE. 



Fructification : spoirs contained in favel- 

 lidia immersed in the frond ; tctraspores 

 collected in imbedded sori ; and " nema- 

 theciaj' tubercles composed of radiatino- 



filaments (anthoridia ?). C crispus becomes 

 horny when dry, and is the liish moss or 

 Carrai/een of the shops. 



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

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

 Brit. pi. 15. 



CHOR'DA, Stackh.— A genus of Larai- 

 nariaceae (Fucoid Algte), with fronds of 

 a pecidiar, simple cylindrical form ; two 

 species, CjHutnanil Clomeiitaria, ?iYe 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- 

 7'anr/es {spores, Harvey, pr»7//;e«K<^«, Ag.) 

 and trichosporatKjes, {cmtheridia, 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. HarveV, Br. Mar. Ah/. 31, pi. 3 B; 

 Pht/c. Brit. 107, &c. ; Thuret, Ann. Sc. Nat. 

 3 s'er. xiv. 240, pi. 29. figs. 5-10 ; Derbes 

 and Sober, Ann. Sc. Kat. 3 ser. xiv. 208, 

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

 28 & 29. 



CHORDA DORSA'- 



i 



a- 



Fio-. 126. 

 LIS, or NoTociioRD. — ° 



The embryonic represen- 

 tative of the spinal co- 

 lumn of the Yertebrata ; 

 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 comparati-vely Magnified 350 diam. 



thick and firm structure- Portion of the chorda 

 1 1 p  „ dorsalis of the embryo 



less membrane, forming „f^ ^^eep, rather more 

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

 cleated cells, which fill sheath; 6, ceUs. 

 the sheath (fig. 120). In 

 some instances, however, its structure is 



