ADIPOSE TISSUE. 



Ixv 



Fig. XXXIII. 



in whom the black matter of the choroid is wanting, the cuticle and the 

 hair are colourless also. 



In some situations the pigment-cells become irregular and jagged at their 

 edges, or even branch out into long irregular processes. Such ramified 

 cells are very common in many animals. In the human body pigment-cells 

 of this description are found in the dark tissue 

 on the outer surface of the choroid coat, lamina 

 fusca (fig. XXXIIL, a a), and on the pia mater 

 covering the upper part of the spinal cord. The 

 condition of the pigment in the hairs will be 

 afterwards described. 



When the cuticle of the Negro is removed by 

 means of a blister, it is renewed again of its 

 original dark hue ; but if the skin be destroyed 

 to any considerable depth, as by a severe burn, 

 the resulting scar remains long white, though it 

 at length acquires a dark colour. 



Uses. In the eye the black matter seems obviously 

 intended to absorb redundant light, and accordingly 

 its absence in Albinos is attended with a difficulty of 

 bearing a light of considerable brightness. Its uses in 

 other situations are not so apparent. The pigment of 

 the cuticle, it has been supposed, may screen the sub- 

 jacent cutis from the pungency of the sun's rays, but 

 in many animals the pigment is not only employed to 

 variegate the surface of the body, but attaches itself 

 to deep-seated parts. Thus, in the frog the branches 

 and twigs of the blood-vessels are speckled over with 



it, and in many fish it imparts a black colour to the peritoneum and other internal 

 membranes. 



Fig. XXXIIL RAMIFIED 

 ' PIGMENT - CELLS, PROM 



THE TISSUE OF THE CnO- 



B.OID COAT OP THE EYE ; 

 MAGNIFIED 350 DIAME- 

 TERS (after Kb'lliker). 



, cells with pigment ; b, 

 colourless fusiform cells. 



ADIPOSE TISSUE. 



The human body in the healthy state contains a considerable amount of 

 fatty matter of different kinds. Fat, as has been already stated, is found 

 in the blood and chyle, and in the lymph, but much more sparingly. It 

 exists, too, in several of the secretions, in some constituting the chief ingre- 

 dient ; and in one or other of its modifications it enters into the composition 

 of certain solid textures. But by far the greater part of the fat of the body 

 is inclosed in small cells or vesicles, which, together with their contained 

 matter, constitute the adipose tissue. 



This tissue is not confined to any one region or organ, but exists very 

 generally throughout the body, accompanying the still more widely distri- 

 buted cellular or areolar tissue in most though not in all parts in which the 

 latter is found. Still its distribution is not uniform, and there are certain 

 situations in which it is collected more abundantly. It forms a considerable 

 layer underneath the skin, and, together with the subcutaneous areolar 

 tissue in which it is lodged, constitutes in this situation what has been 

 called the panniculus adiposus. It is collected in large quantity round 

 certain internal parts, especially the kidneys. It is seen filling up the 

 furrows on the surface of the heart, and imbedding the vessels of that organ 

 underneath its serous covering ; and in various other situations it is depo- 



