IXANITION OF THYROID IX KAT8 323 



indicates little or no loss in absolute weight during' inanition. 

 Tliei'e was found, however, in a larger series of observations an 

 apparent loss of al)out 22 per cent in the weight of the thyroid 

 gland during ehronic hianition (Jackson '15 a). 



In the sei-ies studied, the structure of the thyroid varied con- 

 siderably, but on the whole the changes appear to be essentially 

 similar to those already described for the younger rats held at 

 maintenance (really in a condition of chronic inanition). 



Xo constant difference was apparent between the adults with 

 acute and those with chi'onic inanition. The thyroid follicles are 

 usually but little if any reduced in size. The colloid usually ap- 

 })ears nearly normal in amount and structure, and colloid makes 

 up a large portion of the gland. The cells are frecjuently cuboidal 

 in the central jiortion of the gland, but on the average somewhat 

 reduced in height. Also, especially in the few cells not reduced 

 in size, the cytoplasm usually assumes a ]ir()nounced coarsely 

 vacuolar structure ('hydropic degeneration'), which probably 

 signifies 'an increase in water with a reduction in the amount of 

 living substance. The nuclei frecjuently appear but slightly re- 

 duced in size, and show a marked tendency to hyperchromatosis 

 (various stages of jiycnosis), more rarely hypochromatosis (kary- 

 olysis). In the fi'equent advanced stages of degeneration, des- 

 (luamation of the follicular ejiithelium with obliteration of the 

 follicles occurs as ])re\'iously described in the normal adult gland 

 (fig. 10). Since these degenerative changes occur also in the 

 normal (control) rats, they could not be considered a result of 

 the experiment, except that they usually appear much more ex- 

 tensive and ]:)ron()unced in the I'ats subjected to inanition. In 

 the younger rats, however, as we have seen, the degenerative 

 changes occur much less frequently in the normal rats, and the 

 3^ounger animals are therefore more satisfactory for the experi- 

 ment. 



The stroma of the thyroid in adult rats as a rule shows little 

 change during inanition, although there is some tendency to in- 

 ci-ease in amount, with slight edema (k^ss marked than in the 

 younger rats). There is also frequently a slight hyperemia, es- 

 pecially in degenerating areas. The inci-ease in the volume of 



