330 C. M. JACKSON 



mal albino rats. In a young rat (121 days), the structure was 

 found nearly normal, the epithelial nuclei rarely showing incipi- 

 ent pycnosis. In 2 older rats, however, (200 and 452 days), 

 there was found a considerable amount of epithelium showing 

 desquamation and typical degenerative changes. In the thy- 

 roid of a gray rat (said to be a hybrid gray-albino) sent by Pro- 

 fessor Evans, of the University of California, the structure was 

 found nearly normal, but a few areas showed typical degenera- 

 tion with partial desquamation of the epithelium. 



Through the courtesy of Professor Bensley and Mr. Burgett, 

 I obtained mounted specimens from 8 thyroids of normal albino 

 rats (body weight 117 g. to 287 g.) from the University of Chi- 

 cago laboratories. Of the 8 glands, 2 showed extensive follicu- 

 lar degeneration, 1 moderately extensive and 2 very small areas 

 of slight degeneration. Only 3 appeared perfectly normal 

 throughout. 



Concerning the degenerative appearances found in the thyroid 

 gland. Dr. Bensley writes: 



There are two circumstances which should be borne in mind in con- 

 nection with these changes in the thyroid gland, which frequently, I 

 think, are responsible for similar changes in tissues which were normal 

 to start with, namely: drying of the surface of the gland when adec^uate 

 care is not taken in transferring to weighing l^ottles; and pinching with 

 forceps in the process of extraction. The latter frequently initiates a 

 rapid change in the cell which is marked by acid reaction to indicators, 

 and by greater- affinity for basic stains in the fixed preparation, with 

 loss of characteristic structure by the nucleus. 



In connection with the suggestion by Dr. Bensley of the im- 

 portance of traumatic injury during the removal of the organ in 

 producing degenerative changes, the observations of Sutherland 

 ('15) upon pycnotic changes in nuclei of the spinal cord near 

 the seat of injury may be cited. 



From the foregoing, it appears that the characteristic follicular 

 degeneration of the thyroid appears to a variable extent in ap- 

 parently normal rats, both wild and albino, in widely separated 

 localities. 



Summing up the literature cited, together with my own ob- 

 servations, we may conclude that the thyroid gland shows an 



