THE DUCTLESS GLANDS. , 4OI 



forming three zones : an outer or zona glomerulosa, middle or zona 

 fasciculata, and inner or zona reticularis. The columns are supported 

 by strands of connective tissue in which lie numerous capillaries ; the 

 cells are polyhedral, the cell substance being clear and often containing 

 lipoid globules. 



The cells of the medulla are arranged in an irregular network, their 

 protoplasm being granular and often pigmented. The blood supply of 

 the gland is extremely abundant, particularly in the medulla, in which 

 the interstices of the network of cells are occupied by large sinusoids 

 in intimate relation with the medullary cells. The glands are supplied 

 with nerve fibres from the semilunar ganglia, and a few scattered nerve 

 cells are present. 



The medullary cells contain a substance which stains brown with 

 chromates, and which, on account of its affinity for chromates, has been 

 described as chromaffine material. This is also found, apart from the 

 suprarenal glands, as small masses of tissue (paraganglia) lying along 

 the large abdominal blood-vessels, and in or close to the sympathetic 

 ganglia. The amount of this accessory chromaffine substance varies 

 greatly in different groups of animals. 



The cortical and medullary parts of the glands have a different 

 origin, the cortex being developed from mesodermic tissue (the Wolffian 

 body), whereas the medulla is ectodermic, forming part of the primitive 

 sympathetic system, from which it finally becomes separated and 

 differentiated. In some fishes the cortical and medullary tissue persist 

 as anatomically separate organs, and it is not known whether their 

 coalescence into a single organ in mammals implies any physiological 

 relationship between them. 



In 1855 Addison pointed out that, in man, a disease of which the 

 chief symptoms are prostration, muscular wasting, vomiting, and 

 pigmentation of the skin, and which ends fatally, is associated with 

 disease or atrophy of the suprarenal glands. This observation was soon 

 followed by the study of the effects of their removal in animals ; and it 

 was found that, in mammals, removal of the glands was followed by 

 death in two or three days. 



Subsequent investigation has thrown but little light on the functions 

 of the cortical part of the gland, beyond the fact that tumours of the 

 cortex are sometimes associated with abnormally precocious sexual 

 development. In fishes the removal of the interrenal body, which 

 corresponds in structure and origin with the cortex of the mammalian 

 suprarenal gland, is said by some observers to cause death, though 

 others deny this. 



The medulla contains a substance, adrenalin, tfhich can be ex- 



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