116 



The Endocrine Organs 



observers. Degener finds the increase in weight directly proportional to 

 the time which has elapsed after removal of thyroid (in rabbits). The 

 hypertrophy produced by thyroidectomy affects all parts, but most the pars 

 anterior, in which it is not uncommon to observe a development of colloid- 

 containing vesicles not unlike those of the thyroid : the same appearance is 

 seen in myxoedema (Hale White) and other affections involving atrophic 

 changes in the thyroid, or interference with its function, in the human 

 subject. A. E. Livingston found thyroid feeding to prevent the increase in 



size of the pituitary which 

 would be caused by thy- 

 roidectomy. 



Another striking effect 



of thyroidectomy upon the 



** ?*^HmP5''> a& ^lyj^^H Wt pituitary is increase of 



h. -'. *' flR «'"' ♦• Q ■$!&£< .■<*'■ hyaline and granular 



I «&#-'■ w» $ « ^? * ^-.'fc masses in the pars inter- 



'^VLJKks media, and their passage 



in large numbers through 

 the pars nervosa into the 

 infundibular extension of 

 the third ventricle (fig. 81) 

 (Herring). This denotes 

 an increased activity of the 

 pars intermedia. Whether 

 the phenomenon also occurs 

 in myxoedema has not been 

 noted, but it will probably 

 be found to be the case. 



Halpenny and Thomp- 

 son describe enlargement of 

 the pituitary, and a con- 

 siderable increase of colloid-containing vesicles in the pars intermedia, as 

 the result of parathyroidectomy also. 



The pituitary colloid is not identical with that of the thyroid. It is 

 noteworthy that it does not contain iodine, which is a characteristic com- 

 ponent of the thyroidal colloid in all animals. Even many months after 

 thyroid removal Sutherland Simpson and Andrew Hunter were unable to 

 detect the least trace of iodine in the sheep's pituitary. The pituitary 

 cannot take the place of the thyroid in animals affected with cachexia 

 thyreopriva, nor is pituitary extract able to take the place of thyroid 

 extract in the treatment of goitre and myxcedema. There is, therefore, no 

 evidence that these two organs act vicariously. The effect of the injection 

 of their extracts is, moreover, entirely different. But that they have a 

 certain similarity of function in relation to growth and development is 

 shown by the results of their removal in young animals. In both cases 



Fig 



81. — Section through infundibular recess and neck of 

 posterior lobe of pituitary of a rabbit killed three months 

 after removal of thyroids. Magnified 200 diameters. 

 (Herring.) Cells and colloid bodies streaming through 

 the pars nervosa and passing into the infundibular recess. 



