70 LIFE: ITS NATURE AND ORIGIN 



if some is present). Both complete and partial deficiencies may be 

 single (for one vitamin) or multiple (for more than one vitamin). The 

 deficiency may be either absolute or conditioned. An absolute 

 deficiency is one in which no known environmental conditions enable 

 the organism to synthesize the vitamin from simple foods and nutri- 

 ents; a conditioned deficiency means that under some conditions the 

 organism can synthesize the vitamin and under others it cannot. 



The synthetic ability of a fungus for a particular vitamin may be 

 complete, incomplete or zero. For example, Aspergillus niger has 

 complete synthetic power for thiamine; it can make this substance if 

 supplied with sugar and mineral salts. On the other hand, Phytoph- 

 thora cinnamomi or Ceratostomella from the London plane tree must 

 be supplied with thiamine as such. Between these two extremes of no 

 synthetic power and complete synthetic ability there exist many types 

 of incomplete synthetic power. For example, Mucor Ramannianus 

 can make the pyrimidine half of the thiamine molecule but not the 

 thiazole portion; Ceratostomella pini can make the thiazole but not 

 the pyramidine part, and Ceratostomella montium can combine the 

 two intermediates into thiamine but is incapable of making either. 



Among the filamentous fungi deficiencies for thiamine are common, 

 biotin deficiencies are numerous, pyridoxine deficiencies are infre- 

 quent, inositol is a growth substance for some and oleic acid for one. 

 Beadle and his associates have developed numerous mutants of 

 Neurospora deficient for a variety of vitamins and for specific amino 

 acids. 



The potency of many biological trace substances appears from 

 the following: One part of adrenaline in a thousand million can 

 produce a visible effect on the isolated gut of the rabbit. Pro- 

 fessor Reid Hunt 11 expressed the results of his experiments with 

 acetylcholine thus: one grain (originally the weight of a single 

 grain of wheat) is capable of lowering the blood pressure of a 

 thousand million cats, but this dosage might not kill a single cat. 

 Professor A. J. Clark 12 observes that the spindle-shaped heart cell 

 of the frog measures about 130 by 10 microns (volume about 3400 

 cubic microns), and the acetylcholine molecule measures about 

 1.5 millimicrons. Professor Otto Loewi (Nobel prize 1936) showed 

 that the nerves of the vagus (pneumogastric) reduce heart action 

 by liberating acetylcholine around the heart cells, and Clark esti- 

 mates that a few thousand of these molecules are sufficient to 

 depress a single cell. "The relation in size is similar to that 

 between a large whale (100 tons) and a midge ($ mg)." 



The tables of vitamins and hormones presented at the end of 



