520 



SCIENCE. 



[N. S. Vol. XIV. No. 353. 



visible structure as a germ by usiug the 

 phrase structureless germs. ISTow one ma- 

 terial system can differ from another only 

 in the configuration and motion which it 

 has at a given instant. To explain differ- 

 ences of function and development of a germ 

 without assuming differences of structure 

 is, therefore, to admit that the properties of 

 a germ are not those of a purely material 

 system." 



The dilemma thus put by Clerk Maxwell 

 is (first) that the germ cannot be structure- 

 less, otherwise it could not develop into a 

 future being, with its thousands of char- 

 acteristics; or (second) if it is structural it 

 is too small to contain a sufficient number 

 of molecules to account for all the char- 

 acteristics that are transmitted. A third 

 alternative might be suggested, namely, 

 that the germ is not a purely material sys- 

 tem, an alternative that is tantamount to 

 abandoning all attempts to solve the prob- 

 lem by the methods of science. 



It is interesting to inquire how far the 

 argument of Clerk Maxwell holds good in 

 the light of the knowledge we now possess. 

 First, as regards the minimum visible. The 

 smallest particle of matter that can now be 

 seen with the powerful objective and com- 

 pensating eyepieces of the present day is 

 between the 400V00 and the goirooo of 

 an inch, or 2W0T0 of a millimeter in di- 

 ameter, that is to say, five times smaller 

 than the estimate of Helmholtz of 4^00" 

 of a millimeter. The diffraction of light in 

 the microscope forbids the possibility of 

 seeing still smaller objects, and when we 

 are informed by the physicists that the 

 thickness of an atom or molecule of the 

 substances investigated is not much less 

 than a millionth of a millimeter, we see 

 how far short the limits of visibilitj' fall of 

 the ultimate structure of matter. 



Suppose, then, we can see with the high- 

 est powers of the microscope a minute 



particle having a diameter of 



of a 



millimeter, it is possible to conceive that 

 some of the phenomena of vitality may be 

 exhibited by a body even of such small di- 

 mensions. The spores of some of the mi- 

 nute objects now studied by the bacteriolo- 

 gist are probably of this minute size, and it 

 is possible that some may be so minute that 

 they can never be seen. It has been ob- 

 served that certain fluids derived from the 

 culture of microorganisms may be filtered 

 through thick asbestos filters, so that no 

 particles are seen with the highest powers, 

 and yet those fluids have properties that 

 cannot be explained by supposing that they 

 contain toxic substances in solution, but 

 rather by the assumption that they contain 

 a greater or less number of organic par- 

 ticles so small as to be microscopically in- 

 visible. I am of opinion, therefore, that it 

 is quite justifiable to assume that vitality 

 may be associated with such small particles, 

 and that we have by no means reached 

 what may be called the vital unit when we 

 examine either the most minute cell or even 

 the smallest particle of protoplasm that can 

 be seen. This supposition may ultimately 

 be of service in the framing of a theory of 

 vital action. 



Weismann in his ingenious speculations 

 has imagined such a vital unit to which he 

 gives the name of a biophor, and he has 

 even attempted numerical estimates. Be- 

 fore giving his figures let us look at the 

 matter in another way. Take the average 

 diameter of a molecule as the millionth of 

 a millimeter, and the smallest particle vis- 

 ible as the ^o^^-g-Q of a millimeter. Im- 

 agine this small particle to be in the form 

 of a cube. Then there would be in the side 

 of the cube, in a row, fifty such molecules, 

 or in the cube 50 x 50 x 50 = 125,000 mole- 

 cules. But a molecule of organized matter 

 contains about fifty elementary atoms. So 

 that the 125,000 molecules in groups of 

 about fifty would number i^|^^^ = 2,500 

 organic particles. Suppose, as was done 



