7S-t 



SCIENCE. 



[N. S. Vol. XX. No. 519. 



obtaining nitrates from the nitrogen of the 

 air is of importance also for chemical in- 

 dustry, and it is not impossible that chem- 

 ists may one day utilize the experience 

 obtained in nitrifying bacteria. 



With the discovery of the culture of 

 nitrifying bacteria we have already en- 

 tered the field of Pasteur's work. Yeast 

 had been used for the purposes of fer- 

 mentation before Pasteur, but Pasteur 

 freed this field" of biology just as much 

 from the influence of chance as Liebig 

 did in the case of agriculture. The chem- 

 ist Pasteur taught biologists how to dis- 

 criminate between the useful and harmful 

 forms of yeast and bacteria, and thus ren- 

 dered it possible to put the industry of 

 fermentation upon a safe basis. 



In recent times the fact has often been 

 mentioned that the coal fields will be ex- 

 hausted sooner or later. If this is true 

 every source of available energy which is 

 neglected to-day may one day become of 

 importance. Professor Hensen has recog- 

 nized the importance of the surface of 

 the ocean for the production of crops. 

 The surface of the ocean is inhabited by 

 endless masses of microscopic organisms 

 which contain chlorophyl and which are 

 capable of transforming the radiating en- 

 ergy of the sun into chemical energy. 



Not only through the industry of fer- 

 mentation and agriculture has technical 

 biology asserted its place side by side with 

 physical and chemical technology, but also 

 in the conquest of new regions for civiliza- 

 tion. As long as tropical countries are 

 continually threatened by epidemics no 

 steady indixstrial development is possible. 

 Biology has begun to remove this danger. 

 It is due to Koch if epidemics of cholera 

 can be suppressed to-day and to Yersin if 

 the spreading of plague can now be pre- 

 vented. Theobald Smith discovered that 

 the organisms of Texas fever are carried 

 by a certain insect, and this discovery has 



had the effect of reducing and possibly in 



■ the near future destroying two dreaded 



diseases, namely, malaria and yellow fever. 



It is natural that the rapid development 

 of technical biology has reacted beneficially 

 upon the development of theoretical biol- 

 ogy. Just as physics and chemistry are 

 receiving steadily new impulses from tech- 

 nology, the same is true for biology. The 

 working out of the problems of immunity 

 has created new fields for theoretical biol- 

 ogy. Bhrlich has shown that in the ease 

 of immunity toxins are rendered harmless 

 by their being bound by certain bodies, 

 the so-called anti-toxins. The investiga- 

 tion of the nature and the origin of toxins 

 in the case of acquired immunity is a new 

 problem which technical biology has given 

 to theoretical biology. The same may be 

 said in regard to the experiments of Pfeifer 

 and Bordet on bacteriolysis and hemolysis. 

 Bordet's work has led to the development 

 of methods which have been utilized for 

 the determination of the blood relationship 

 of animals. 



VIII. 



The representatives of the mental sci- 

 ences often reproach the natural sciences 

 that the latter only develop the material 

 but not the mental or moral interests of hu- 

 manity. It seems to me, however, that this 

 statement is wrong. The struggle against 

 superstition is entirely carried on by the 

 natural sciences, and especially by the ap- 

 plied sciences. The nature of superstition 

 consists in a gross misunderstanding of 

 the causes of natural phenomena.' I have 

 not gained the impression that the mental 

 sciences have been able .to reduce the 

 amount of superstition. Lourdes and 

 Mecca are in no danger from the side of 

 the representatives of the mental sciences, 

 but only from the side of scientific medi- 

 cine. Superstition disappears so slowly 

 for the reason that the masses as a rule are 

 not taught any sciences. If the day comes 



