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DAVID MAKINE 



exhaustive jtages, and especially in exophthalmic goiter, the stroma may 

 become strikingly prominent (this will be discussed more fully under 

 Atrophies). Brissaud, Erdheim (a.), Farner. 



Involutionary or Recovery Stage. Involutionary or recovery changes 

 may begin at any stage of the hyperplasia. They may occur sponta- 

 neously or may be markedly hastened by the administration of iodin. 

 The end stage of involution is the colloid or resting thyroid (this will be 

 discussed more fully later). The process of involution may be arrested at 

 any stage and active hyperplasia begin again. We must recognize all de- 

 grees of this regressive or 

 involutionary stage from 

 the marked hyperplasia 

 back to the colloid gland, 

 just as one must recognize 

 all degrees of the progres- 

 sive or actively hyperplas- 

 tic change from the normal 

 or colloid gland up to 

 marked hyperplasias. The 

 anatomical changes are, 

 therefore, the reverse of 

 those described under "De- 

 veloping Hyperplasias," 

 and are briefly as follows: 

 The gland as a whole be- 



Fig. 11. Moderate active hyperplasia, thyroid comes firmer to the touch, 

 common fowl (Gallus domesticus) illustrating the rni Pn l or phaiio-pci fmm 

 disappearance of colloid and the infoldings of the Ganges 



high columnar epithelium. gray-red and opaque of 



the marked hyperplasias 



to gray-red and translucent, to reddish translucency and finally to the 

 translucent amber-red of the colloid or resting stage. The blood supply 

 diminishes. This is associated with a lessening of the caliber of both the 

 arteries and veins due to a thickening of the vessel walls similar to that 

 observed in the involuting thymus or uterus. The alveoli become visible 

 to the naked eye. They appear as enlarged, rounded, highly variable sized 

 cavities containing colloid. The colloid at first but palely staining and 

 granular, gradually becomes more uniform, more dense, stains more in- 

 tensely and finally comes to resemble in all respects the colloid of the nor- 

 mal thyroid. Paralleling the colloid accumulation, the high columnar 

 epithelium with its infoldings and plications slowly returns to columnar, 

 to cuboidal and finally to flat cuboidal if the involution is complete, while 

 the infoldings take on more of the appearance of small tufts of stroma 

 jutting into the alveolar space and covered with the prevailing type of al- 

 veolar epithelium. The stroma becomes less prominent either by compres- 

 sion or absorption, and when the gland returns fully to the colloid state, the 



