Febeuaey 26, 1915] 



SCIENCE 



309 



their products. On the other hand, Dn- 

 claux^ believes that an organism becomes 

 less vigorous when its growth is continued 

 upon media in which some of its products 

 exist. Thibaut,^" LeSage^^ and Nikitin- 

 sky,^^ have studied auto-association. Their 

 results however do not lead to the same 

 conclusions, although they are explicable 

 and constant. There is to be found from 

 Thibaut a suggestion that the existence of 

 fermentation products favors growth of 

 yeasts. Penicillium grown on its own cul- 

 ture does not reach fructification, says Le- 

 Sage. Then, too, Nikitinsky found favoring 

 conditions when molds are cultivated upon 

 media containing their own products. He 

 noticed as well that antagonistic influences 

 are manifested if the media contain cer- 

 tain carbonaceous substances, even stat- 

 ing that in the presence of carbonaceous 

 foods, probably lactic acid, butyric acid and 

 alcohol are at times responsible for stimu- 

 lation or retardation. Wildier^^ has intro- 

 duced the "Bios Fraga. " Contrary to 

 the views of Pasteur, he claims that minute 

 quantities of yeast will not grow in the 

 medium of yeast ash, ammonium salts and 

 some sugar. He contends that the element 

 introduced by the addition of greater 

 amounts of yeast for inoculable material is 

 required. He also says that it is a sub- 

 stance very soluble in water, dialyzable, 

 difficult to alter or precipitate, and is found 

 no longer after incineration. It is a sub- 

 stance which exists in small quantities and 

 is indispensable. To this is attached a 

 sort of mysticism which would lead one to 



9 Duelaux, Traite de Microbiologie, Paris, I. 

 and III., 1898 et 1900. 



10 Thibaut, Cent. f. BaU., Ab. 11., Bd. 9, S. 743, 

 1902. 



iiLeSage, Travaux soientifiques de I'Univer- 

 site de Eeimes, I., p. 171, 1902. 



12 Nikitinsky, JaJiri. wiss. Sot., 1904, Bd. 40, 

 S. 1. 



isWildier, Le Cellule, T. 18, p. 313, 1901. 



recognize some hidden guard within the 

 impregnable fortress of life. 



In infectious diseases, there are indica- 

 tions of self-curbing or restrictive devel- 

 opment. There appear to be some influ- 

 ences acting in the cases of many pathogens. 

 For instance, the organisms which give rise 

 to influenza, whooping cough and measles 

 and others run their courses; they have 

 their rise and reach their maximum stage 

 of development, and then decline in their 

 activity. Others, as tuberculosis and 

 glanders, appear to be accelerated by their 

 extended development in the body. Again, 

 there is the type which may be designated 

 in general by organisms which are trans- 

 mitted through carriers or are commensals. 

 Whether an organism reacts upon itself 

 through its growth in media which are fer- 

 mentable, or in the body of an animal 

 where disease is produced, or where the 

 body acts only as a carrier, is it not pos- 

 sible to discern a common functional prin- 

 ciple responsible? 



Conjunctive association seems also to 

 designate another subclass which, for the 

 time being, may be called "serial associa- 

 tion." One species seems to follow upon 

 the heels of another in point of time, and is 

 dependent upon the other for its life and 

 activity. Sometimes these species appear 

 to grow together simultaneously, but in 

 nearly every case the life and activity of 

 the one depends in sequence upon the life 

 and activity of the other. One seems to be 

 the leader and the other the dependent. 

 There are instances, perhaps, where the 

 relationship between the two suggest an 

 interdependence. In this case, both may be 

 leaders and both dependents. I do not 

 know of a case that has been worked out 

 in detail confirming this peculiar rela- 

 tionship, although observation may suggest 

 it. It may be assumed that in such a case 

 products which are favorable to each are 



