CARTILAGE. 41 



ether or strong alcohol, the fat may be extracted from the vesicle, which is 

 then seen empty and shrunken. 



Besides the fully-formed fat-cells above described, others may occasionally 

 be found in the course of formation, especially in cases of sudden death during 

 robust health. They are described by Rollett as, in the first stage, small round 

 granular cells, provided with a roundish nucleus, into the interior of which a 



Fig. 12. 



Adipose tissue, a. Starlike appearance, from crystallization of fatty acids. (High power.) 



strongly refracting drop of fat is then secreted, which is at first surrounded by 

 a ring of the granular matter, and gradually increases so as to fill the cell. As 

 the granular matter becomes less and less, the nucleus, which can at first be 

 easily recognized, becomes less perceptible, but according to this author can 

 always be brought into view by appropriate reagents. Fat is said to be first 

 detected in the human embryo about the fourteenth week. 



In various parts of the body pigment is found, viz., in the hairs, in the iris 

 and choroid coat of the eye, in the lungs, in the nerve-cells, in the rete mucosum 

 in the dark races, and in some parts of the body such as the areola of the 

 nipple which are of dark color even in the fair races, except Albinoes, in 

 whom pigment is absent. Pigment-cells are also found in the blood, according 

 to Virchow. 



In many situations the color is produced simply by the presence of dark 

 granules scattered about without any definite arrangement ; in the -choroid coat 

 the pigment forms a regular layer of hexagonal nucleated cells filled with 

 pigment granules ; in other parts the pigment is contained in branching cells, 

 probably the connective-tissue-corpuscles filled with pigment granules ; and in 

 most situations, such as the nerve-cells and the epidermis, the pigment-granules 

 form a greater or less element in the contents of the nucleated cells of the part. 

 In the dark races the color of the skin is due to the accumulation of pigment 

 in the deeper layers of the epidermis the rete mucosum. 



CAKTILAGE. 



Cartilage is a non- vascular structure which is found in various parts of the 

 body in adult life chiefly in the joints, in the parietes of the thorax, and in 

 various tubes, such as the air-passages, nostrils, and ear, which are to be kept 

 permanently open. In the foetus at an early period the greater part of the 

 skeleton is cartilaginous. As this cartilage is afterwards replaced by bone, it 

 is called temporary, in opposition to that which remains unossified during the 

 whole of life, and which is called permanent. 



