74 ADAPTATION AND DISEASE 



organism with its many activities they are evidently present in 

 another form ; living matter, therefore, as I have expressed it 

 elsewhere, contains as an essential constituent proteidogenous 

 rather than proteid matters. 



The Structure of the Proteins 



But the structure of these proteins, as worked out first by 

 Curtius and Schutzenberger, and as more fully demonstrated 

 by Ernil Fischer through the actual synthesis and building up 

 of bodies of protein nature in the laboratory, is highly significant. 

 They are molecules so large that they will not pass through fine 

 filters, giant molecules but a little below the limit of visibility 

 under the highest powers of the microscope. Take one of the 

 simpler crystallizable proteins, namely Haemoglobin, its com- 

 position appears to be approximately C yi2 H ngo N FeS , 

 in fact, the average molecular weight of proteins has been 

 estimated at about 15,000, or, roughly, one thousand times that 

 of a molecule of water. And the haemoglobin from each species 

 of vertebrate is a different chemical substance, nay more, our 

 researches in immunity indicate that there may be differences 

 between the haemoglobins of two members of the same family. 

 Certainly no two analyses of separate samples of crystalline 

 haemoglobin obtained from the same species give identical 

 results. By digestion, as every board school child knows, we 

 break these proteins down into peptones and albumoses. By 

 further disintegration Kossel and others have broken down 

 these peptones and protones into their constituent amino-acids, 

 bodies belonging to the fatty acid series — aminated fatty acids. 

 What Fischer has done has been to manufacture these aminated 

 fatty acids (acetic, propionic, etc.) in the laboratory, and 

 then he has accomplished the reverse process of linking these 

 together, until with five, ten, fifteen, and more linked together 

 he has obtained bodies affording the chemical tests for 

 peptones. 



Now these amino-acids have one striking property — they are 

 amphoteric ; they possess both acid and basic properties, acid 

 because of the contained COOH group or groups, basic through 

 the NH 2 group or groups. Thus we conceive these peptones 



