160 ANIMAL PHYSIOLOGY. 



part of the chest. In its early history it is closely associated 

 with the thyroid, but its structure is different in detail. 



Fig. 84. THYROID AND THYMUS BODIES, three months before birth. 

 a, Thyroid body resting on trachea and larynx ; 6, 6, thymus ; 

 c, c, lungs, as yet unexpanded; d, heart. 



It reaches its greatest development in infancy, and dis- 

 appears usually with childhood. Its 

 function, supposed to be connected 

 with blood-elaboration, is unknown. 



The suprarenal capsules, are a pair 

 of bodies surmounting the kidneys, 

 and fitting on to their upper ends. 

 Like the thymus, they are exceedingly 

 large before birth. They are highly 

 vascular in the interior, but are like- 

 wise remarkable for their copious 

 supply of sympathetic nerves, and it 

 Fig. 85. SUPRARENAL is scarcely safe to 'say that they are 

 CAPSULE AND KID- blood- elaborating glands at all. All 

 NEY, three months that is known about them is, that 

 before birth; the kid- there ig a pecu li ar f orm o f wasting 

 ney presenting at this -,. . T ..-. * , 



period a lobulated Disease accompanied with deep bronz- 

 surface. ing of the skin, in which there is fre- 



