236 B. F. KINGSBURY AND PAULINE E. HIRSH 



12). With iron hematoxylin they retain the stain strongly as do 

 the nucleoli. The application of a more differential stain, such as 

 the Biondi-Heidenhain shows that the}^ are not basi-chromatin 

 (figures 20, 21). In the next stage the nucleus 'runs together' 

 into a more or less compact mass in which however the chromatin 

 and parachromatin portions are usually distinguishable. Very 

 often the latter in some globular form adheres to the chromatin 

 mass as though 'squeezed out' (achromatic body of Hermann). 



There are many forms of the degeneration picture. Quite 

 common is the typical chromatolytic — or preferably and more 

 correctly karyolytic — nucleus described by Heidenhain ('90) in 

 which the chromatin collects peripherally as a shell, series of 

 globules, or very often a crescent, the achromatic mass being 

 central. Figure 9 shows one of these inadequately while figures 

 18 and 19 give them in more detail. The condensation and corre- 

 sponding shrinking of the nucleus during this stage is usually exces- 

 sive so that a considerable space intervenes between the nucleus 

 and the cytoplasm, which throughout appears scanty and consists 

 largely of a peripheral layer which may be connected with the 

 nuclear mass by strands. 



Further changes consist in the dissolution by fragmentation 

 (and liquefaction?) together with a loss of staining power with 

 basic stains. The resulting mass of granular and globular debris 

 contains much fat which is undoubtedly responsible for many of 

 the vacuoles apparent in figures 7 and 8. 



Significance. In considering the significance of these degener- 

 ations the first thought would be that they were pathological— 

 a result of an infection or an abnormality introduced into the life 

 conditions (lack of oxygen, insufficient circulation, etc). This, 

 indeed, is the interpretation of Driiner, who believed that the 

 degenerations were caused by protozoa infesting the nucleus and 

 causing their degeneration. His figures and descriptions how- 

 ever are not conclusive and in the absence of any experimental 

 evidence and in the light of the occurrence in Desmognathus of 

 these degenerations, at a specific time and in a specific region 

 such an interpretation becomes highly improbable. Likewise 

 there is no indication of interference with the blood supply which 

 might cause their degeneration secondarily. 



