CHAPTER II 



CONSTITUENTS OF THE BIOSPHERE 



As LONG as chemistry retained its aura of secrecy and magic ; that is, up to 

 the seventeenth century, the study of the chemical compounds making up 

 the biosphere had not even been considered. One may attribute the first 

 step to Van Helmont who, in his work Ortus medicinae, pubhshed in 1652, 

 described carbonic anhydride as being present in intestinal gases, separated 

 an alkaline substance from blood and attempted to resolve human urine 

 into its constituents. It was necessary to await the development and 

 elaboration of the idea of chemical compounds before Scheele, in 1775, 

 succeeded in isolating uric acid from urinary' calculi and PouUetier de la 

 Salle, in 1782, extracted cholesterol from gall-stones with the aid of alcohol. 

 Following this came the most spectacular period of organic chemistry 

 which saw the establishment of the idea of "radicals" (groups of atoms in 

 the molecule which can be considered as remaining intact throughout a 

 series of reactions, and which can be transferred from one molecule to 

 another without undergoing disruption) and the idea of chemical type 

 (that two substances which possess similar chemical properties have a 

 similar arrangement of their constituent atoms in the molecule). The 

 application of methods capable of isolating substances present in living 

 things without any gross chemical changes taking place resulted in the 

 identification of a large number of these constituents and the list of these 

 increases daily. In 1862, Ernest Wagner, professor at Leipzig, in his 

 Manual of General Pathology, stated an important generalization — that, of 

 the material of living substances, apart from water, a large percentage can 

 be divided into three simple organic types which we recognize today as 

 fatty acids, sugars and amino acids. - A mushroom, a spinach leaf, a sea 

 urchin egg, the flesh of an oyster, a silk- worm, contain respectively 91*3, 

 92'3, 77-3, 88*3, and 78-4% of water. The dry residue is made up of these 

 three principal types of compounds to the extent of 94-2% in the mushroom, 

 72-6% in the spinach leaf, 93-5% in sea urchin egg, 90-5% in oyster flesh 

 and 83-9% in the silk- worm. The spinach leaf contains a somewhat smaller 

 proportion of these organic constituents than the others due to the larger 

 amounts of inorganic material which amounts to 27-2% of the dry weight. 

 The sea urchin egg, on the other hand, contains only 1*5% of inorganic 

 matter, mainly chlorides, sulphates, phosphates and bicarbonates of 

 sodium, potassium, calcium and magnesium. Nevertheless, as stated above, 



