4 8 BACTERIOLOGY. 



ence of the cells producing them are, so to 

 speak, " active " proteid, a kind of intermed- 

 iate stage between lifeless " nutritional " pro- 

 teid and living cells. Active proteid possesses 

 another property which has become recognized 

 through the medium of bacteriological inves- 

 tigation, that, namely, of killing bacteria and 

 influencing the activity of bacterial poisons. 

 This property of " activity " is acquired by 

 virtue of the vitality of the cell, but is to 

 some extent independent; it can outlast the 

 mother cell and may be preserved for some 

 time by the addition of chloroform, carbolic 

 acid, cresol, or toluene, or by careful drying, 

 while heat, light and putrefaction destroy it. 

 It is a fact of interest in this connection that, 

 according to Scholl, such an " activity " which 

 has been removed by heat can be partly re- 

 stored by purely chemical measures and thus 

 the distinction between lifeless and living, 

 active and passive proteid still further obliter- 

 ated. 



After all is said, spontaneous generation re- 

 mains up to the present time only an unavoid- 

 able general hypothesis. The attempts of 

 Liebig, Thomson, and Helmholtz to refer the 

 origin of life on our planet to importation from 

 other heavenly bodies evades the question and 

 leaves it as obscure as before. In the synthesis 



