348 Mr. R. H. A. Plimmer [April 8, 



of growth. These two workers further showed that these amino 

 acids are connected with the production of the purine ring in the 

 animal body, i.e. with the production of uric acid. 



The function of the whole group of mono-amino acids has jet to 

 be determined. Are they all necessary ? For glycine we can say 

 that it is not essential, as it is the only amino acid which the animal 

 can synthesise. 



These results remind us of the well-known experiments on the 

 need by plants of all the inorganic elements. Sir Daniel Hall, in his 

 book on " Fertilisers and Manures," gave a striking picture of barley 

 grains grown on a full food and foods lacking one constituent. 



We may thus correlate the amino acid content of proteins for 

 growth of animals with the set of inorganic elements needed for the 

 growth of plants. 



The relative value of various proteins in nutrition has been 

 studied by Osborne and Mendel. In their experience lactalbumin 

 is superior to casein, and casein to edestin. They found that 50 per 

 cent more casein and 90 per cent more edestin were required to 

 produce the same gain in weight ; in other terms, a food containing 

 i) per cent lactalbumin was equal to one with 12 per cent casein and 

 15 per cent edestin. 



Suitable mixtures of proteins have also been tested, and attempts 

 are being made to find out the most suitable addenda for making the 

 proteins of cereals more adequate for the growth of animals, that is, 

 adding what we may call " good " protein to " bad " protein to make 

 the latter efficient as food. Leaf and seed proteins are good as a 

 mixture. 



Economically it may be better to use an expensive protein as 

 food, and produce rapid growth, than to feed for longer periods on 

 poor proteins and get slower growth. 



A simple calculation brings out the problem to be solved. We 

 may wish to build up the casein of milk with 16 per cent of glutamic 

 acid, and we are provided with wheat gliadin with over 40 per cent 

 of this unit. There is waste of glutamic acid. Gliadin further 

 contains 0'2 per cent of lysine, whilst casein contains 6 per cent. 

 To produce this amount we require thirty times as much gliadin, 

 and consequently the waste of glutamic is further increased. 



Cannibalism is the most economical method of protein nutrition, 

 as the amino acids of the food are in the exact proportion required 

 by the tissues. The nearest parallel to this is the nursing of the 

 young animal by its mother : the child actually gets the proteins 

 of the mammary glands. 



Recent work shows that quality of protein is most probably the 

 primary cause of the disease Pellagra, although there are some 

 indications that general insufficiency of protein, together with 

 improper salt supply, are contributory factors. 



Pellagra is a peculiar disease characterised by severe disturbance 



