68 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



Fig. 33. Pigment cells from 

 the choroid coat of the eye. 

 These cells are of connective- 

 tissue origin. 



body connective-tissue pigment cells are limited to 

 the choroid coat and iris of the eye, to birth-moles, 

 and to the piamater of the brain. The pigment 

 may be of any color, the constituent being melanin, 

 a coloring material probably derived from the blood. 



(c) Fat Cells. These are 

 connective-tissue cells with 

 a large storage of fat. The 

 fat occupies the center of 

 the cell as a big drop which 

 crowds the cytoplasm and 

 nucleus to one side, closely 

 pressed against the cell 

 wall, which is unusually 

 conspicuous. The cells 



are large and spherical. Since fat is dissolved by 

 alcohol, these cells in sections are distorted, polyhe- 

 dral, and appear more like irregular spaces than any- 

 thing else. Normal fat is 

 not to be confounded with 

 pathological fat found in 

 fatty degeneration of 

 organs. In the latter case 

 the fat appears as little 

 droplets diffused through 

 the cytoplasm of the dis- 

 eased cells, and is pro- 

 duced at the expense of protoplasm, a destructive 

 process or katabolism. Normal fat is a constructive 

 process or anabolism, and is therefore a storage of food 

 or potential energy. Its production, physiologically, 

 is not clearly understood. It may be produced from 



Fat. 



Cytoplasm. 



Nucleus. 

 Fig. 34. Normal fat cell. 



