THE BASIS OF LIFE 13 



plasm present certain contrasting features. A chemist reaches 

 the compound which he wishes to form by effecting a series of 

 interchanges. For example, he wishes to form uric acid by 

 uniting a nucleus contained in lactic acid with urea. First 

 he introduces chlorine and ammonia into the molecule of 

 lactic acid. He makes trichlorlact amide. Then he heats 

 (supplies energy to) a mixture of trichlorlactamide and urea. 

 Two of the chlorine atoms carry off hydrogen atoms from 

 the urea. A third leaves the trichlorlactamide with its 

 ammonia. Water also breaks away. Uric acid remains. 



Trichlorlactamide Urea Uric Acid 



CC1 3 CH.OH.CO.NH 2 +2(NH 2 ) 2 CO = C 5 H 4 N 4 3 + NH 4 C1 + 

 2HC1 + H 2 0. 



In this example the trichlorlactamide may be said to exchange 

 its chlorine and ammonia for urea. When he planned the 

 reaction, the chemist foresaw what would happen. He 

 knew that if he weakened the grip of the lact radicle upon 

 them, chlorine and hydrogen, chlorine and ammonia, oxygen 

 and hydrogen, would take the opportunity of getting away 

 together. The lact radicle and urea would be left with dangling 

 arms, which must " satisfy their affinities " by linking up. 

 It would be rash to assert that any reaction is impossible to 

 Nature's chemistry ; but it may safely be said that the reactions 

 which protoplasm effects are, so far as we know them, of a 

 different type from this laboratory example. Uric acid is the 

 chief excrement of birds. It is made in the liver. If the 

 liver is shut off from the circulation, lactate of ammonia is 

 excreted in the place of uric acid. It is therefore, in all proba- 

 bility, lactate of ammonia which the liver transforms into 

 uric acid. We cannot pretend to say how this is done, although 

 an empirical formula for the change might be drafted easily 

 enough. 



Lactate of ammonia has the formula NH 4 ,C 3 H 5 3 . Uric 

 acid, C 5 H 4 N 4 3 , contains a much higher percentage of nitrogen. 

 It could be produced from lactate of ammonia by the con- 

 densation of the nitrogen-containing nucleus and the addition 

 of a sufficient amount of oxygen to complete the oxidation 

 of the superfluous carbon and hydrogen into carbonic acid and 

 water. It is of little interest to count the number of atoms 



