1908-9. ] ON THE ORIGIN OF LIFE ON THE GLOBE. 435 
the same manner as particles of dust which float in the path of a sun- 
beam are revealed. If one were to stand in the course of a sunbeam 
and look toward the source of the light, namely the sun, no floating 
dust particles would be seen but if one stands aside in the dimly lighted 
room and looks at the beam the dust particles come out very clearly, 
for the light which is reflected from the numerous facies of each comes 
to the eyes as divergent rays and the dust particles are thus seen greatly 
magnified. Quite so in the ultramicroscope the light instead of coming 
from the reflector under the microscope straight through the micro- 
scope to the eye, is sent obliquely through the object, which in this case 
is a drop of colloid solution, the particles in suspension of which scatter 
the light as the dust particles do in the sunbeam and in consequence 
some of the divergent rays passing up the tube of the microscope and 
reaching the eye reveal the particles as greatly magnified flashing 
points of light. In fact the particles in such a case set against the dark 
background of the field appear like as if they were bright stars set in 
the cloudless, moonless night sky. 
The ultramicroscope will not reveal the presence of particles less 
in diameter than one-hundredth of a micron, that is, less than one-two 
million five hundred thousandth part of an inch, so that the limits of 
ultramicroscopic vision are 1/7 and 1/100 of a micron. What their true 
measurement may be in the case of protein solutions we do not know 
but Mr. E. F. Burton* has, by an ingenious method, determined that 
the suspension particles of colloidal solutions of gold, platinum and 
-silver have a diameter which ranges between 2/100 and 6/100 of a 
micron. It is not unlikely that these represent also the limits in the 
diameter of the particles in protein suspension solutions. 
Now the significance of these particles comes out strikingly when 
it is recognized that protoplasm is constituted of myriads of such sus- 
pension particles of protein closely packed together and that the proper- 
ties of living matter, that is, protoplasm, are the properties also of each 
Suspension particle present in it. Each particle in protoplasm is in a 
definite sense alive just as is the protoplasm as a whole and consequently 
though it may not continue to live after its separation and isolation 
from its fellows because there has developed amongst them an inter- 
dependance, it is conceivable that ultramicroscopic particles consisting 
of but a few molecules of protein appropriately constituted could live 
separately and reproduce themselves by division when the particles had 
grown beyond a certain size. 
*Phil. Mag., Vol. (6), II, p. 425, 1905. 
