GLOSSARY 301 



diffusion, absorption, chemical reaction, electrical 

 effects, surface tension, hydrolysis, double decom- 

 position, and formation of solid and colloidal films. — 

 Chem. Did. 



Spectrometer. A spectroscope (i.e., an optical in- 

 strument for producing and analyzing spectra) that 

 is fitted with special appliances for the measurement 

 of wave-length of spectral lines, etc. 



Spontaneous Generation. Until about the middle 

 of the seventeenth century, besides the belief in the 

 doctrine of special creations, the belief in the spon- 

 taneous generation of various life-forms, which was 

 handed down from antiquity, was very general; in 

 the church as well as without. When, about 1660 

 A.D., Francesco Redi, an Italian court physician, 

 demonstrated that the maggots of flies grow from 

 eggs, and not spontaneously from putrefying mat- 

 ter, it was — to use the words of a writer in Man — 

 "the accepted notion, that scorpions were generated 

 by sweet basil, that frogs were brought by heavy 

 rain, that cabbages brought forth butterflies, and 

 that a mulberry tree could engender silkworms." 

 But experiments to prove or disprove spontaneous 

 generation continued to be made for two hundred 

 years. All these experiments, however, merely had 

 to do with sterilization. Pasteur (-1-1895) was fore- 

 most among the men who finally disproved the old 

 ideas. When perfect sterilization had been secured, 

 the belief in spontaneous generation was discarded 

 for the belief: Omne vivum ex vivo. 



Surface Tension. The tension of a liquid caused 

 by the attraction exerted upon the surface mole- 

 cules by the molecules lying underneath, and mani- 

 festing as the tendency of all liquids to contract to 

 the minimum area and to act as if they were sur- 

 rounded by a very thin membrane. 



