602 THE THYMUS. [Book ii. 



suggest on the one hand that important metabolic processes 

 take place in them, some of which are probably connected with 

 the history of the pigments of the body at large. On the other 

 hand the unusually large nerve supply, and the derivation of 

 part of the body from the sympathetic ganglia, suggest pecu- 

 liar nervous connections. And the organ has often served as 

 a starting point for speculations in these two directions; but 

 our exact knowledge concerning them is very limited. By 

 experiment we learn that removal of the whole of both supra- 

 renal bodies entails speedy death, the symptoms having a general 

 resemblance to those due to the removal of the thyroid. The 

 removal of one suprarenal alone is inadequate to produce this 

 result; and the symptoms following removal of both may be at 

 least mitigated by injection of an extract prepared from the 

 organ. This suggests a function of the suprarenals analogous 

 to that of the thyroid. Injection of the extract of suprarenals 

 in adequate doses also produces distinct physiological effects, 

 notably constriction of the blood vessels and inhibition of the 

 heart. 



One fact, gained by clinical experience, pointing in the 

 same direction is of great interest. Disease of the suprarenal 

 bodies, apparently tubercular in nature and beginning in the 

 medulla, is so often associated with a change in the colour of, 

 with an increase of the pigment of the skin, ' bronzed skin,' 

 'Addison's disease,' that some connection between the two 

 must exist; but the several links of the chain are as yet 

 unknown. It is tempting to associate the increase of pigment 

 in the bronzed skin with the fact that the suprarenal body con- 

 tains some substance or substances, possessing striking colour 

 reactions, giving a dark blue or dark green colour with ferric 

 chloride, and a carmine red tint with various oxidizing agents; 

 but we have no exact knowledge at present. 



§ 395. The Thymus. This, again, is essentially a lymphatic 

 structure, and indeed might be regarded as a part of the lym- 

 phatic system. 



From the thymus there may be extracted by means of saline 

 solution a form of a peculiar proteid, a so-called nucleo-albumin 

 which, like the corresponding bodies from lymphatic glands or 

 from leucocytes, seems to have some special relations to the for- 

 mation of fibrin. Thus, as has already been said (§ 22), a solu- 

 tion of this body from the thymus, injected into the veins, will 

 give rise to extensive intravascular clotting. 



The thymus, like the other bodies on which we are now 

 dwelling, is also rich in extractives. Thus xanthin, hypoxan- 

 thin, leucin, lactic, succinic and other acids have been found 

 in it. 



But of what really takes place in the body we have no exact 

 knowledge. Since the thymus is best developed before birth, 





