COLLOMIA. 



[ 156 ] COLOURING MATTERS. 



(fig. 22 c), at others they contain carbonate 

 and phosphate of lime (fig. 22 d). Sometimes 

 they exhibit a radiate appearance (fig. 22 e). 

 In the liquid form, colloid exudation is 

 found within cysts in the thymus and thyroid 

 glands, the ovary, &c. ; and within the 

 enlarged areolse of areolar tissue around 

 these organs, &c. It is found in a free 

 state upon the surface of inflamed serous 

 membranes. 



The colloid corpuscles are met with in the 

 hypertrophied heart, in the prostate (both 

 male and female), the thyroid and the thymus 

 glands, in the choroid membrane, in the 

 brain and spinal cord, and in the (waxy) 

 spleen, &c. 



The liquid colloid matter generally consists 

 of a proteine- compound ; it becomes of a 

 gelatinous consistence, retaining its trans- 

 parency, or turbid and opake, by heat. The 

 colloid corpuscles do not, however, appear 

 to be uniform in composition; sometimes 

 they consist of a proteine-compound ; at 

 others, probably, of cellulose or amyloid, as 

 in the brain (true CORPORA AMYLACEA). 

 These bodies are further noticed under the 

 heads of the tissues and organs in which 

 they occur. See also TUMOURS (Colloid 

 cancer}. 



BIBL. Rokitansky, Handb. d. Path.Anat. 

 bd. 1. p. 304; Wedl, Grundzuge d. Path. 

 Histol. ; Forster, Hand. d. Spec. Path. ; 

 Virchow, Arch. f. Path. Anat. v. ; Hassall, 

 Micr. Anat. &c. 



COLLOMIA, Nutt. A genus of Polemo- 

 niacese (Dicotyledons) remarkable for the 

 spiral structures produced in the epidermis 

 of the seeds (PI. 21. fig. 22) (see SPIRAL 

 STRUCTURES). The gummy substance in 

 which fibre is imbedded is soluble in water 

 and not in spirit, therefore the best way to 

 observe the elastic opening of the spiral 

 fibres is to make fine sections of the coat of 

 the seed and place them in a little spirit of 

 wine, upon a slider, with a covering glass : 

 to adjust the focus, and then to add water 

 carefully at the side of the covering glass so 

 as to wash away or dilute the spirit. 



COLOSTRUM. The first liquid secreted 

 by the mammary glands. See MILK. 



COLOUR. See INTRODUCTION, p. xxix. 



COLOURING MATTER, OF ANIMALS. 

 See PIGMENT. 



COLOURING MATTERS, OF PLANTS. 

 The green colour of vegetables depends upon 

 the presence of CHLOROPHYLL, and is 

 spoken of under that head. The red and 

 yellow colours assumed by leaves and herba- 



ceous shoots in autumn, depend upon a 

 chemical metamorphosis of the chlorophyll, 

 or on its absorption and the discoloration of 

 the cellular tissue. The red colour presented 

 by many of the lower Algae, such as some of 

 the Palmellacese, appear also to depend upon 

 a metamorphosis of the chlorophyll, con- 

 nected with the vital processes ; it is met 

 with also in the contents of the resting 

 spores of many of the filamentous Confer- 

 voids. We have found the protoplasm assu- 

 ming a reddish colour in the punctum 

 vegetationis of the buds of Monocotyledons 

 in the autumn, which probably depends upon 

 a similar cause. The bright colours of 

 flowers and other parts of the inflorescence 

 of plants, as also of the lower surface of 

 many leaves (Begonia, Victoria, &c.) and 

 herbaceous shoots, arises from the presence 

 of matters of a different kind, almost always 

 dissolved in the watery cell-sap. The colour 

 of petals is ordinarily found to depend upon 

 a certain number of the cells subjacent to 

 the epidermal layer being filled with a 

 coloured fluid ; and the depth of the colour 

 is proportionate to the number of superim- 

 posed layers of such cells, which act like so 

 many layers of a pigment. Each cell is 

 usually filled with one colour when fully 

 developed, but adjacent cells are often seen, 

 in variegated petals, to contain distinct 

 colours, the line of demarcation being accu- 

 rately fixed by the cell-walls, through which 

 the colours do not transude, unless the cells 

 are injured by pressure. In young tissues 

 the colour often has a granular appearance 

 in the cells, but this is a deception arising 

 from the mode in which the colour is deve- 

 loped. The colourless protoplasm originally 

 filling the cells becomes excavated, as it were, 

 by water bubbles, and the watery contents 

 of the excavations become coloured; they 

 gradually enlarge, as the protoplasm applies 

 itself more completely to the walls of the 

 cell, until they become confluent and the 

 coloured liquid fills the whole cell-cavity. 

 We have observed this pseudo-granular 

 appearance in the cells of the flowers of 

 Orchis Mono, in the cells of the lower 

 surface of the leaf of Victoria, and other 

 cases. 



In some cases the liquid colouring matters 

 of flowers have been found to contain solid 

 corpuscles; the red colour-cells of Salvia 

 splendens, and the blue ones of Strelitzia 

 regina, contain globules, and according to 

 von Mohl, this is still more commonly the 

 case with the yellow colours ; in the yellow 



