IODINE. 



[ 367 ] 



ISARIA. 



ture mth those of the small intestines, except 

 that they are larger and broader in propor- 

 tion to the greater thickness of the mucous 

 membrane. The solitary follicles also differ 

 from those of the small intestine in their 

 larger size, and in the cu'cumstance that 

 each of the minute elevations of the mucous 

 membrane produced by them exhibits a 

 rounded or elongated opening, leading to a 

 depression in the mucous membrane over 

 the follicle (fig. 377). This, however, has 



Fig. 377. 



Magnified 45 diameters. 



Solitary follicle from the colon of a child, a, tubular 

 glands ; b, muscular coat of the mucous membrane ; c, 

 submucous tissue ; d, transverse muscular fibres ; e, pe- 

 ritoneum ; /, depression in mucous membrane over the 

 follicle a. 



no communication with the follicle. 



The investigation of the structure of the 

 intestines is a matter of some difficulty. The 

 epithelium must be examined in a perfectly 

 fresh state. The glands are most readily 

 seen in portions hardened by absolute alco- 

 hol or chromic acid ; whilst some have re- 

 commended boiling with acetic acid (80 per 

 cent.), then diying and making sections with 

 a Valentin's knife. The muscular elements 

 are rendered most distinct by maceration 

 with dilute nitric acid (20 per cent). 



The capillaries of the intestines are very 

 beautiful when injected ; but great care is 

 required in securing the vascular branches 

 to prevent the escape of the injection. 



BiBL. Kolliker, Mikrosk. Anat. ii. and 

 the Bibl. therein given. 



IODINE. — Solution of iodine is often 

 useful for dyeing and rendering very trans- 

 parent objects more distinct, and for its 

 producing with some vegetable and animal 

 tissues and substances colours by which 



they may be distinguished. The general 

 results of its action are enumerated in the 

 Introduction, p. xxxviii, and special re- 

 marks are made under the heads of the 

 tissues. 



An aqueous solution of iodine is the best 

 for general use, but a solution in spirit is 

 much stronger. A very strong solution may 

 be made by dissolving iodine in a solution 

 of iodide of potassium. See also Schulz's 



LIQUID. 



IRID^A, Bory. — A genus of Cryptone- 

 miaceae (Florideous Algae), containing one 

 British common species, I. edulis, a dull red 

 obovate, leaf-shaped sea-weed of fleshy-car- 

 tilaginous texture, 4 — 18" long, the central 

 substance composed of longitudinal filaments, 

 the cortical of closely-packed moniliform 

 perpendicular filaments. Fructification : 

 spores in spherical masses (favellidia), im- 

 bedded in the frond in wide patches near the 

 extremity; tetraspores in dense band-like 

 immersed sori. 



Bibl. ll?cv\ey, Brit. Mar. Alg. 150. pi. 19, 

 A; Phyc. Brit.\^\. 97; Greville, Alg. Brit. 

 pi. 17 ; Engl. Bot. pi. 1307. 



IRIDESCENCE. See Introd. p. xxx. 



IRIS. See Eye, p. 252. 



ISARIA, Hill. — A genus of Isariacei 



Fig. 378. 



Fig. 378. Isaria citrina. Plants on a fungus. Nat. size. 



Fig. 379. 



Fig. 379. Isaria citrina. A single plant, showing the 

 fruit. Magn. 20 diams. 



(Hyphomycetous Fungi), growing upon dead 



