198 ./. J. Christian 



severe (Dempsey, 1948; Sayers and Sayers, 1949; Greep and Deane, 

 1949b) . The lipid vacuoles disappear first from the fasciculata next to the 

 reticularis, so that it becomes indistinguishable from the latter. As stimula- 

 tion continues, the disappearance continues centrifugally, and at the same 

 time enzymes normally absent from the fasciculata, but present in the 

 reticularis, make their appearance in the cells of the fasciculata, the inner- 

 most portion moving outward (Symington et at., 1958). Upon withdrawal 

 of the stimulus of ACTH the lipid vacuoles increase considerably in size 

 and may become very large. This stage presumably represents lipid storage. 

 The cellular hyperplasia and hypertrophy mainly account for increases in 

 the size and weight of the adrenal glands. Initially the cortex responds to 

 stimulation with a marked decline in its cholesterol, neutral lipids, and 

 ascorbic acid content (Greep and Deane, 1949b; Sayers and Sayers, 1949). 

 These soon return at least partially to their original state, and in the inac- 

 tive gland they may exceed their original levels. These matters are dis- 

 cussed in detail in the cited references in addition to discussions therein of 

 the relationships of the cortex and its activity to various stimuli for varying 

 lengths of time and with varying intensity. 



c. The adrenal medulla. The adrenal medulla consists of rather irregular 

 masses of polyhedral chromaffin cells derived, along with the ganglia of 

 the sympathetic nervous system, from the primitive neuroectoderm. The 

 medulla is homologous with the sympathetic ganglia and receives myeli- 

 nated cholinergic preganglionic fibers from the greater splanchnic nerve. 

 The medulla itself serves as the ganglion and the postganglionic tracts. 

 There apparently are several types of cells in the medulla; these are dis- 

 cussed in more detail elsewhere (Hartman and Brownell, 1949; Eranko and 

 Raisanen, 1957) . The cytoplasm of the medullary cells contains numerous 

 minute deeply basophilic granules which stain blue with ferric chloride 

 and brown with chromic acid (chromaffin) and which appear in some way 

 to be related to secretory function. 



The adrenal medulla generally is not thought to hypertrophy following 

 stimulation in the same way that the adrenal cortex does. Rogers and 

 Richter (1948) reported the absence of medullary hypertrophy with 

 changes in adrenal size in rats. However, there is good evidence that the 

 medulla does hypertrophy, at least in some species and under some circum- 

 stances, even though it may not contribute significantly to an increase in 

 the total weight of the gland, as a consideration of its geometry will show. 

 House mice have been shown to exhibit a marked medullary hyperplasia 

 and hypertrophy during pregnancy (Tamura, 1926) or chronic stimulation 

 due to crowding (Bullough, 1952). Medullary hypertrophy also has been 

 observed in a variety of species of captive wild ungulates subjected to 

 conditions in a zoological garden similar to the crowding of mice reported 



