EFFETE PRODUCTS. 75 



Cholenterin, C 26 H U O, exists throughout the body where active 

 tissue change is going on, particularly the nervous centres. It is 

 a inonatomic alcohol, and is the only one existing free in the body. 

 It may be obtained from gall stones, some of which consist entirely 

 of cholesterin. It may occasionally be found in a crystallized 

 form in. any of the fluids of the body normal or pathological 

 (except the tears and urine), but it only seems to be an effete 

 product, nearly all that produced in the body being discharged 

 along with the effete portions of the bile. It may be recognized 

 by the shape of the crystals, which are rhombic plates, in which 

 one corner is generally deficient. 



Effete Products. 



These, as has been stated before, are generally the outcome of 

 the active chemical changes necessary for the growth and vitality 

 of the living protoplasm, and are for the most part soon elimi- 

 nated by the excretory glands, so that but small quantities of 

 them can be found in the active tissues where they are produced. 



Urea, CO(NH 2 ) 2 , is the most important constituent of the 

 urine of mammalia, but not of that of birds or reptiles. Traces 

 of it may be found in the fluids and tissues of the body. It is 

 readily soluble in water and alcohol, and forms crystals when its 

 solution is concentrated. It decomposes when treated with some 

 strong acids or alkalies, taking up water and yielding CO 2 and 

 NH 3 , and with nitrous acid gives CO 2 -f N -(- H 2 O. It was the 

 first of the so-called " organic " compounds to be made artificially, 

 being obtained by Wo'hler in 1828 by mixing watery solutions 

 of cyanate of potassium and sulphate of ammonium, evaporating 

 to dryness and extracting with alcohol, or, in short, by heating 

 cyanate of ammonia with which it is isomeric. 



CN ) CO") 



Ammonium Cyanate = N H 4 > = H 2 > N 2 = Urea. 

 J H 2 ) 



It can now be produced artificially in other ways. 



It has also been considered to be a diamide of carbonic acid 

 (CO(OH) 2 ), the two atoms of hydroxyl being replaced by two 

 atoms of amidogen, NH 2 , thus (CO(NH 2 ) 2 ). In the presence 



