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elastic. The color varies from a pale translucent amber-red to a bright 

 amber-red? The blood vessels are much enlarged, usually tortuous, and 

 their walls are thickened. On section, the alveoli vary greatly in size as 

 compared with the normal, which are much more uniform. The smallest 

 are much smaller than the smallest seen in a normal, and the largest are 

 many times larger than the largest alveoli seen in the normal gland. All 

 the alveoli are* filled with a clear amber-yellow colloid, which gives to the 

 thyroid its characteristic translucency. Microscopically the epithelium is 



Fig. 18. Colloid goiter in man 

 (from case of clinical exophthalmic 

 goiter), illustrating the lymphoid 

 hyperplasia, the irregular size of the 

 alveoli, uniform colloid and low 

 cnboidal epithelium. (After Marine 

 and Lenhart, Arch. Int. Med., 1911 : 7.) 



Fig. 19. Moderate active hyperplasia, 

 thyroid of dog. (After Marine, J. Infect. 

 Dis., 1907: 4.) 



low cuboidal. The sprig-like projections (remnants of the old infoldings 

 and plications) can be made out. These are more distinct in recent 

 involutions than in long standing colloid glands. The stroma is increased, 

 although there are exceptions depending on the extent of the fibrosia 

 occurring during the stage of active hyperplasia and the extent of its 

 absorption during the process of involution. Hyaline transformation is 

 not infrequently seen. The arterial walls are always thickened and 

 historically show an obliterating endarteritis similar to that seen in 

 the involuting thymus or uterus. The stainable colloid is of normal 

 density and distribution in the alveoli. The percentage of iodin in the 

 colloid gland may be as high as that of a normal thyroid, though usually 

 it is somewhat lower. (See Figs. 1G, 17, 18.) 



The administration of a few milligrams of iodin daily to an animal 

 with a hyperplastic thyroid causes a rapid involution to the colloid or rest- 

 ing stage. This reaction is illustrated in Figures 19, 20 and 21. Hitzig, 

 Kocher, A., Sanderson-Danberg, Wegelin, White, Wolfler. 



