672 INTERNAL SECRETION ENDOCRINE GLANDS 



within a few days or weeks largely because they refuse to eat. Polyuria 

 (increase of urine beyond the normal) does not necessarily occur. It 

 is well known that when only one kidney is extirpated the other hyper- 

 trophies, and no ill-effects ensue. 



The statement that extracts of the kidney when injected into the 



veins of an animal cause a rise of arterial blood-pressure, essentially 



through direct action on the peripheral vaso-motor mechanism, is of 



considerable interest, for it may possibly have some bearing on the rise 



of pressure and consequent hypertrophy of the heart associated with 



certain renal diseases. But there is not as yet sufficient evidence that 



the hypothetical pressor substance, to which the name ' renin ' has 



been given, in any sense represents an internal secretion of the kidney. 



.^^ The pressor substance (so-called 



^JpM||L ' urohypertensine ') which can be 



Jfr ^\ extracted by ether from normal 



^Jf \ human urine (Abelous) is probably 



Ajyt^Mr \| only excreted by the kidney, and 



KP^^ ^\ ^.^ perhaps arises from the putrefac- 



\jM|N ^ on * proteins in the intestine. 



If For it has been shown that in the 



putrefaction of (horse-) meat bases 



U^^ rijfrf 



, _ blood-pressure. The most active 



Fig. 219. Injection *of Extract of Bone- of these is a body known as 

 Marrow with the Vagi Cut. To be read ^-hydroxyphenylethylamine, 

 from left to right. formed from tyrosin (Barger and 



Walpole). Whether the pressor 



(vaso-constrictor) substance which appears to be liberated from the 

 platelets when blood is shed, and may therefore be presumed to be more 

 slowly liberated from such platelets as normally break down in the 

 circulating blood, has any relation to the pressor substance of urine 

 is unknown. It is also quite uncertain whether, as has been stated by 

 some observers, extracts of the kidney or blood from the renal vein 

 stave off for a time the onset of the uraemic symptoms that follow 

 removal of both kidneys or ameliorate them when they have already 

 appeared. 



Spleen. The spleen does not produce an internal secretion 

 necessary to life, for it can be removed both in animals and in 

 man, without the development of serious symptoms. Its blood- 

 forming and blood-destroying functions (p. 22) are taken on by 

 other structures (particularly the red bone-marrow). 



The most definite changes following splenectomy are transient 

 anaemia, increased resistance to haemolytic agents, and an increase 

 in the content of cholesterol in the blood (Pearce). These effects 

 are more pronounced in the young. This is intelligible if the spleen 

 normally plays a considerable part in the destruction of worn-out 

 erythrocytes with liberation of haemoglobin, the source of the bile- 

 pigment. The formation of the bile-pigment is said to be inter- 

 fered with, and its amount reduced by more than 50 per cent. 

 (Pugliese). 



The spleen can be auto-transplanted readily into the subcutaneous 

 tissues of animals. There is a great difference in the behaviour of 



