222 ON VARIABILITY AND ADAPTATION 



having done this, he has succeeded in Unking them together in 

 series. In one case he linked together as many as eighteen 

 amino-acid radicles. These polypeptides, as he has termed them, 

 in appearance, reactions (such as the characteristic Biuret 

 reaction, which we use commonly to detect the presence of 

 proteins), and in behaviour towards acids and alkalies, so closely 

 resemble the true peptones that, to quote Fischer, they must 

 be regarded as their nearest relatives. And Fischer has gone 

 further than this. In the Faraday lecture delivered by him in 

 London in 1907, he announced that one of the bodies artificially 

 built up by him (I. leucyl- triglycyl- I. tyrosin) has all the pro- 

 perties of the albumoses — of certain simpler proteins which we 

 gain by the peptic and tryptic digestion of muscle. 



\ 



/ \> ■ \ d> ^ 



o 



/ C <H T H-CH-COf^ \ \ ^* 



c % ' co ^ - 



C.H.OH A Cl p 



< *°>*» „ A SPA* TI0 



TYROSIN. * 



Fig. 19. 



Thus at last there has been accomplished the building up of 

 these specific organic substances which in nature are found solely 

 as the outcome of life — nay more, form the material basis for 

 the manifestation of life. It is the most notable achievement 

 of the new century. 



Here let me again emphasize the fact that these proteins 

 which we are now in a position to build up, or, if you like 

 the term, manufacture in the chemical laboratory, are inert 

 bodies. They are not living as we understand the term : the 

 living matter is not proteid, but proteidogenous. Can we form 

 a chemical or physical conception of the difference between the 

 two — between living and dead organic matter ? 



"Here is a fact, the meaning of which is of far-reaching 

 significance. I show you two tubes. Each contains a small 



