316 ANATOMY FOR NURSES [Chap. XVI 



trachea. It is described as a temporary organ of foetal and infantile 

 life. It appears at the end of the second month of intra-uterine 

 life and continues to grow until a child is two or three years old. 

 At that time it weighs about six drachms. Thereafter it atroj)hies 

 and disappears, except for some shreds of tissue still present at 

 the age of puberty. The function of this gland is not known, but 

 it is thought to have a definite connection with growth and with 

 the development of the reproductive organs. 



(4) The adrenals or supra-renal capsules. — The adrenals are 

 small flattened bodies of a yellowish color wliich are ])laced one 

 above each kidney. They are usually classified with the ductless 

 glands, as they have no excretory duct, but are sometimes classed 

 with the organs of the central nervous system, as they contain a 

 great deal of nerve-tissue. Each organ weighs about one tlrachm, 

 and is invested by a fibrous capsule which sends fibres into the 

 glandular substance ; these fibres form a framework for the soft, 

 I)ulpy substance of the gland, and within the spaces of the frame- 

 work are groups of cells. (See Fig. KHL) 



The adrenals are plentifully supplied witli ])lood-vcssels and 

 lymphatics, and they contain some striking coloring matters. 

 In diseases of these organs, the skin frequently becomes " bronzed " 

 from an increase of pigment or coloring matter. 



Function. — The adrenals produce an internal secretion which 

 is called adrenalin. The function of this secretion seems to be con- 

 nected with maintaining the tone of the heart and blood-vessels. 

 It is still a question whether this maintenance of tone is the result 

 of the secretion acting directly on the tissues of the heart and blood- 

 vessels, or indirectly on the nerve centres. Removal of these 

 glands results in such a loss of tone that death follows. 



Adrenalin extract is made from the supra-renal capsules of ani- 

 mals, and is used as a heart stimulant to improve the tone of the 

 heart and blood-vessels, also in hemorrhage to constrict the vessels. 



(5) The hypophysis. — The hypophysis, also called the pitui- 

 tary body, is of an ovoid form, a reddish gray color, and consists of 

 two lobes. The anterior lobe is larger and distinctly glandular, 

 the posterior lobe is smaller and composed of nerve cells and 

 fibres. 



The pituitary is lodged in a depression of the middle portion 

 of the sphenoid bone, and is firmly held in place by the dura mater. 



