ii2 SYMBIOSIS 



to those forming our own bodies. We want in fact symbiotic 

 cross-food or spare-food capital, which contains the vital amino- 

 acids fit for reciprocity in ideal association with other indispen- 

 sable " export " material of the plant. It is partly because of 

 our long-standing transgression against the norm of feeding that 

 we are provided with the cumber of a long digestive tract, which 

 serves the secondary purpose of separating the useful from the 

 unnecessary in our diets. 



Elimination and the further fate of the absorbed amino- 

 acids is thus described by Dr. Alsberg : 



As ordinary diet may contain more nitrogenous material than is 

 needed by the organism, a part of the amino-acids is changed within the 

 walls of the intestinal canal by the removal of the amino-group to form 

 ammonia. As this takes place in the presence of carbonic acid, ammonium 

 carbonate and ammonium carbamate are formed. It has recently been 

 found that there is an equilibrium between these two substances, so that 

 where one is present in solution there is also found a definite amount 

 of the other. It is an easy step from ammonium carbamate to urea. 

 Thus the amino-group split off from the amino-acid in the intestinal wall 

 or elsewhere is ultimately converted into urea and excreted. There are 

 probably other methods of the formation of urea, as, for example, by 

 cleavage from arginine which contains a guanidine grouping closely related 

 to urea. After the removal of the amino-group from the amino-acids 

 there is left a carbonaceous residue which may be burned to furnish 

 energy, perhaps directly, perhaps after conversion into sugar. A portion 

 of the amino-acids absorbed by the intestines is not, however, deprived 

 of its nitrogen, [it is only the " too much nitrogen " that we are to be 

 safeguarded against as long as possible], but passes into the blood stream 

 from which it is absorbed by each individual cell according to that 

 cell's particular needs. [Real or pathological needs, I should, however, 

 add, for it is a notorious fact that as Emerson has stated, we breed men 

 with too much " guano " in their composition, which is saying in other 

 words that many cells have developed exorbitant nitrogen appetites.] 

 The cell then reconstructs from these amino-acids its own characteristic 

 protein. [The reduction process being accomplished with more or less 

 efficiency, the animal cell at last obtains a modest portion of indispensable 

 " cross-food " and can now, thus impregnated, " generate " its own 

 characteristic, yet in a sense " heterozygous " proteins. " Crossing," 

 in the wider sense, is thus again seen to contain a secret of evolution.] 

 Thus it is possible to explain in a comparatively simple manner how, for 

 example, wheat protein [cross-food] when fed to an animal is converted 

 into the characteristic protein of that animal. It is done by the cells 

 of the tissues from amino-acids supplied to the cells by the blood, the 

 blood receiving the amino-acids from the intestinal wall. 



I should say, however, that the animal receives the amino- 

 acids from the laboratory of the plant by reason of the 



