24 PHARMACEUTICAL BACTERIOLOGY 



fragment having upon its exterior deposits of organic matter with bacteria 

 endospores, and filterable viruses, enter the atmospheric zone of a planet 

 like that of the earth, the resistance offered by the air would at once re- 

 move the now absolutely dry pulverulent germ-bearing portions of the 

 meteor, leaving them behind as a very fine invisible dust which would be 

 very much retarded in its motion toward the earth's surface; somewhat 

 larger particles would follow faster and. become more or less incandescent 

 during their flight through the layer of atmosphere, constituting the 

 fiery trail of the meteor. It is highly probable that the very finest par- 

 ticles, as the germs measuring less than o.o$n. in diameter, would never 

 reach the earth, being prevented from doing so by the earth's electronic 

 (electro magnetic) repulsion. Some spores and micro-organisms would, 

 however, finally reach the earth due to the action of convection currents, 

 electrical action and the direct and reflected repulsion energy (radiation 

 pressure) of light. 



Arrhenius in his book entitled "Worlds in the Making" very lucidly 

 sets forth the pros and cons of the idea of panspermia and his general con- 

 clusion is that the interplanetary dissemination of bacterial spores is 

 within the possible. 



Schwarzschild has determined mathematically that spherical particles 

 measuring o.i/i in diameter are most markedly affected by the radiation 

 pressure of sunlight. As is well known to bacteriologists, the endospores 

 of bacteria do not measure more than from o.2/i to 0.3/1 in diameter, 

 even less in the dry state. The compound microscope reveals living 

 plasmic particles which are less than 0.025 m diameter. The ultramicro- 

 scope enables us to visualize particles of gold and of other minerals in 

 colloidal suspension, which particles are said to approximate molecular 

 dimensions. 



The filterable viruses of yellow fever, rabies, smallpox, the mosaic 

 disease of tobacco, foot and mouth disease of cattle, and others, are even 

 smaller than the endospores. For example the cytoryctes (Cytorhyctes 

 vaccinece) which is presumed to be the primary cause of smallpox, meas- 

 ures from 0.5^ to less than 0.2;* in diameter when suspended in liquids. 

 In the dry state the smaller specimens would measure less than 0.065^ 

 in diameter. 



Very naturally the question arises how long a period of time is re- 

 quired for these pangerms to be carried from one planet to another. 

 It has been determined mathematically that a germ from the earth would 

 reach Mars in twenty days, Jupiter in eighty days, Neptune in fourteen 

 months and our nearest solar system (Alpha in Centauri) in 9000 years. 

 Can spores and low organisms survive these periods and the conditions 

 known to exist in interstellar space? The answer is in the main in the 



