CHEMICAL CONSTITUENTS 289 



lipids are thus able to assume forms which differ as regards 

 their staining and morphological appearance and it is necessary 

 to bear this fact in mind in interpreting anatomical observa- 

 tions. There is a considerable species difference regarding the 

 distribution as well as the composition of the lipids. In 

 some animals (including man) the lipid shows double re- 

 fraction but this optical evidence of anisotropy is absent in 

 the adrenals of some of the lower animals. 



In man the lipids, as observed histologically, seem to be 

 present chiefly in the fasciculata. The reticularis contains 

 smaller droplets while the glomerulosa appears to be free of 

 visible lipids. The fat droplets have a peculiar glistening 

 appearance and show the double refraction referred to above, 

 when observed under a polarizing microscope. After fixation 

 in formalin or bichromate, the lipids are solidified but melt 

 again when heated to 56°C. 157 



In the dog, the glomerulosa is the chief depository of lipids 

 while in the Cheiroptera (bats) the lipids are present chiefly 

 in the reticularis. 362 



Various stains are utilized to demonstrate the presence of the 

 adrenal lipids histologically. Osmic acid stains the droplets 

 black or greyish brown ; sudan and scarlet red, a brilliant orange 

 or red; nile blue, violet or blue. Like myelin, the lipid is 

 stained blue by Weigert's method. 



The adrenal lipids are also characterized by the relative 

 ease with which they are removed from the cells by such sol- 

 vents as xylol, ether, or chloroform. 



The chief constituent of the anisotropic lipid is cholesterol 

 and its esters. Wacker and Hueck 653 found each human 

 adrenal to contain 0.4 per cent of free cholesterol and 0.1 to 

 0.15 per cent of cholesterol esters. However, other substances 

 are also present which contribute to the anisotropic property 

 of the adrenal lipids. Thus Rosenheim and Tebb 135 have 

 isolated stearic and palmitic acids, sphingomyelin (a phos- 

 pholipid), and phrenosin (a phosphorous-free galactosid) from 



