1906.] on The Physical Basis of L/fr. 407 



composes itself to sleep each individual bends round its head and 

 tucks the tip of the l)eak — it is all it can do, poor thing ! — under the 

 dwarfed wing. 



This lingering instinct, this ol)session by the great past, is like a 

 whale dreaming of the green fields in w^hich his forefathers browsed ! 

 Now, each indi^'idual penguin starts life as a microscopic fragment of 

 living matter, a single cell, so wonderfully compounded, so cunningly 

 devised, as to enshrine without loss all the diverse qualities and 

 powers which the word " penguin " connotes, down to the trivial 

 detail I have described ! There is little wonder that the naturalists 

 of half a century ago gave the problem up in despair. There is 

 cause for wonder and for congratulation that, impelled by the divine 

 dipsomania for research, knowledge has moved so far as to make a 

 beginning in the assaults. 



Given a fulcrum, anything can be moved. The necessary fulcrum 

 was found when attention was directed, not, as in Huxley's time, to 

 the more obvious resemblances between the different kinds of proto- 

 plasm, but to the less obvious differences. The microscope for the 

 most part fails us here, in the first place because the discrimination 

 between different kinds of matter by the agency of sight is possible 

 only when there are associated differences in optical properties, and 

 when there is the possiljility of getting a clear image. Now, living 

 matter is singularly free from definite optical differences ; it has the 

 optical characters of ground glass. Therefore, the ultimate refine- 

 ments of microscopic vision are for the most part wasted upon it. 

 The dead cell exhibits remarkable structural details, but in the act 

 of death there is of necessity a redistribution of matter which 

 obscures and defaces the finer details of the real living structure, and 

 replaces them by structure which is formed in the process of dying. 

 For the material basis of the difference in the strains of living 

 matter we have to look below the limits of microscopic vision, below 

 the limits even of the living molecule, to the chemical molecule of 

 which that living matter is built up. 



The nearest chemical approach to living matter is the proteid, 

 the chemical substance of which all protoplasm is, water excepted, 

 chiefly composed. And the fulcrum I spoke of, or, better, the 

 thought which loosed the fetters of imagination, was the appreciation 

 of the significance of the fact that proteids chemically are not all 

 alike, and that the strains of living matter differ from one another 

 in the kinds of proteid of which they are built up — that is to say, in 

 their ultimate chemical constitution. 



All proteids are not the same proteids : there are proteids of 

 men, others of beasts, others of fishes, and others of birds ! 



The nature of the differences leads us to a real picture of the 

 underlying differences betw-een the kinds of protoplasm. The tide 

 of thought of the older observers was fettered by the fact that all 

 proteids have about the same atomic composition. The biologist of 



