THE PATHOLOGICAL ANATOMY 

 Summary 



283 



Summing up the previous four groups or the strictly physiological 

 phases of goiter, it is seen that the thyroid cells have a cycle of morpholog- 

 ical changes and, so far as we at present know, but one cycle. Beginning 

 with the normal or colloid thyroid, this cycle is characterized hy hyper- 



Fig. 20. Section of same thyroid 

 shown in Fig. 19, removed 10 days 

 later. (After Marine, J. Infect. Dis., 

 1907: 4.) 



Fig. 21. Section of same thyroid 

 shown in Figs. 19 and 20, removed 14 

 days later. (After Marine, J. Infect. 

 Dis., 1907: 4.) 



trophy going on to hyperplasia which terminates either in exhaustion 

 atrophy or in involution (recovery). If involution takes place the gland 

 returns to a functionally normal state, and anatomically to the nearest 

 normal condition that the once hyperplastic thyroid can again assume. 

 Anatomically, this state is spoken of as colloid gland (goiter). From this 

 stage, the thyroid may again repeat its cycle through hypertrophy, hyper- 

 plasia and on to exhaustion atrophy or involution. Marine and Lenhart (a) . 



Atrophies 



The thyroid is physiologically active throughout life. Its activity is 

 most pronounced during youth and early adult life and gradually lessens 

 with age. Several forms of simple atrophy within the limits of normal 

 physiology may he recognized, for example, senile atrophy, atrophy fol- 

 lowing castration, the involution of hyperplasias, atrophy from disease and 

 pressure atrophy, de Coulon, MacKenzie, Payne, Yandervelde and Hen- 

 rard. 



Senile Atrophy. This is normally seen in old age and in associa- 

 tion with many wasting diseases as in the late stage of pulmonary tuber- 



