144 TOPOGRAPHICAL ANATOMY OF THE 



the medial border of" the kidneys, generally cranial to the hilus. The 

 right gland lies along the lateral border of the caudal vena cava, the left 

 having a similar relation to the aorta. The right gland is usually more 

 prismatic in form than the left. 



Section of the adrenals reveals a thin fibrous capsule on the exterior 

 enclosing a parenchyma, in which two parts can be readily distinguished. 

 A paler, reddish-brown cortical substance lies immediately underneath 

 the capsule, and a darker, more vascular, and somewhat softer medullary 

 substance occupies a considerable area in the centre of the gland. In 

 the medullary substance it is not difficult to recognise venous spaces 

 with the naked eye. 



The adrenals belong to the group of structures known as the duct- 

 less glands, or, according to more modern nomenclature, endocrine 

 organs ; and their secretion is poured into the blood stream. A material 

 known as adrenalin is elaborated by the cells composing the medullary 

 substance. 



The developmental history of the adrenals is of interest. The 

 cortical substance is derived from the same cells as is the endothelium 

 of the peritoneum. The medullary substance, on the other hand, is 

 apparently developed from the neural crest of the embryonic spinal 

 cord, which also gives origin to the ganglia on the dorsal roots of spinal 

 nerves and the ganglia of the sympathetic nervous system. 



Renal lymph glands (Lymphoglandulae renales). — A small group of 

 lymph glands can generally be demonstrated about the hilus of the 

 kidney. 



Dissection. — With great care remove the fat that lies dorsal to the 

 kidneys and about the aorta as it passes through the diaphragm. The 

 greater and lesser splanchnic nerves are to be sought as they bend round 

 the dorsal border of the diaphragm lateral to the so-called crura of this 

 muscle. 



N. SPLANCHNICUS MAJOR. — The greater splanchnic ^ nerve arises 

 from the sympathetic ganglia within the thorax from the sixth or 

 seventh to the fourteenth or fifteenth inclusive, and enters the abdomen 

 by curving round the dorsal border of the diaphragm (lumbo-costal arch) 

 in relation to the lateral border of the psoas minor nmscle. It ends by 

 joining the coeliaco-mesenteric ganglion. Close to its termination a 

 small splanchnic ganglion is occasionally developed on the nerve. 

 From both the nerve and the ganglion small filaments pass to the 

 oesophagus, aorta and vertebrae. 



N. SPLANCHNICUS MINOR. — The lesser splanchnic nerve is formed 

 1 crirXayxvLKOi (splauchnicos) [Gr.], pertaining to the viscera. 



