310 



SCIENCE 



[N. S. Vol. XLI. No. 1052 



simultaneously created. Where one fol- 

 lows the other, relying upon association 

 products, many illustrations are available. 



Ammonification in the soil usually asserts 

 that protein material has undergone 

 change, yielding a series of products by the 

 action of specific classes of organisms. It 

 is known that sometimes in this series more 

 than one class of organisms is involved. 

 After ammonia is produced, the common 

 oxidation processes resulting in nitrites and 

 nitrates are effected by two distinct classes. 

 Accordingly, in the disintegration of a pro- 

 tein molecule by microorganisms, there are 

 probably several classes involved in the 

 process, each in consecutive order. All of 

 them are dependent one upon the other in 

 the various steps of the degradation of the 

 molecule. Then again, if we were to con- 

 sider the reduction of nitrates to nitrites 

 to nitrogen or ammonium, there are two or 

 three other classes, each waiting its turn 

 in the serial change. 



The different stages in the ordinary de- 

 composition of milk speak of this same 

 dependence. At fii-st the several types in 

 milk appear to foster the development of 

 the lactic organisms ; following in the wake 

 of the lactic organisms are those which 

 neutralize and then those which cause pro- 

 teolytic changes; and if we were to trace 

 out the reduction of the complex substances 

 to the various simple mineral constituents 

 that may be found in the final product, 

 there would doubtless be other classes, 

 similar to those found in the mineralizing 

 actions of the soil. 



In fermentations, too, are well-known 

 examples: the change of apple must to 

 apple wine, from apple wine to vinegar by 

 yeast and acetic bacteria ; the production of 

 ginger beer with a specific yeast and spe- 

 cific bacterium ; the making of ' ' Sake ' ' from 

 rice by means of a mold and a yeast; as 

 well as other well-known fermentations in 



nature, all of which confirm how frequently 

 the life of one organism is dependent upon 

 the life of another. Among the pathogens 

 and those organisms associated with the 

 animal body are many striking instances. 

 The many complications illustrate the pos- 

 sibilities of interdependence — sepsis follow- 

 ing scarlet fever and typhoid fever, diph- 

 theria and pest; pneumonia following in- 

 fluenza and tuberculosis ; gangrene strepto- 

 cocci with certain anaerobic putrefying 

 organisms; pyogenic bacteria and tetanus 

 organisms. We can not be as certain per- 

 haps and as distinctly satisfied as in the 

 fermentations, the nature of which is so 

 well known, that one product follows an- 

 other and definitely in the order mentioned, 

 but that there is a decided infiuence mani- 

 fest can not be gainsaid. When growing 

 together under circumstances of association, 

 the disease is usually aggravated, or one 

 organism appears to pave the way for an- 

 other. It is a kind of serial relationship 

 which parallels very closely, to say the least, 

 those which we find in fermentations. 



This serial dependence is not lost even 

 where host and parasite are concerned. 

 The tick and the cow are indispensable to 

 the piroplasma in the corpuscle; the fly 

 and the antelope to the trypanosoma in 

 sleeping sickness; the mosquito and man 

 to the Plasmodium in malaria ; the bacterial 

 forms and man to the ameba in his intes- 

 tines; the rabbit and some outside habitat 

 to the coccidium. The microorganisms in- 

 volved in these cases are apparently de- 

 pendent upon the metazoa concerned for 

 their growth and cyclic development, very 

 much as the nitric organisms are dependent 

 upon the products produced by the serial 

 changes in the breaking down of the pro- 

 tein molecules. In these eases in which 

 animals furnish the material for the life of 

 microorganisms, difficulties are found in 

 the determination of the required condi- 



