March 23, 1906.] 



SCIENCE, 



471 



tage of it to secure an abundance of speci- 

 mens at little or no cost. 



Chaeles W. Hargitt. . 

 Syracuse University, 

 The ZooLOGicAi Laboratory. 



SPECIAL ARTICLES. 



EFFECT OF DEYINQ UPON LEGUME BACTEEIA. 



The almost simultaneous appearance of 

 Bulletin No. 270 of the Geneva (New York) 

 Experiment Station and Farmers' Bulletin, 

 No. 240 of the IJnited States Department of 

 Agriculture, the one stating that cultures of 

 nodule-forming bacteria dried on cotton were 

 worthless for practical purposes and that the 

 failure of these cultures was inherent in the 

 method of their preparation, the other stating 

 that the Department of Agriculture did not 

 consider cultures dried on cotton entirely sat- 

 isfactory and would instead distribute liquid 

 cultures hermetically sealed, has perhaps nat- 

 urally resulted in unwarranted and unfairly 

 severe criticism toward the cultures dried on 

 cotton. 



The most misunderstood feature in the de- 

 terioration of dried or partially dried cultures 

 is the distinction between the effect of desicca- 

 tion per se and the effect of small quantities 

 of moisture present for some length of time, 

 either because of slow drying or because of 

 absorption of water vapor from a humid at- 

 mosphere after the cotton had been thoroughly 

 and rapidly dried. It has, therefore, been 

 considered desirable to publish at once an 

 explanation of the simple paradox that the 

 rapid drying of cultures of nodule-forming 

 bacteria causes a relatively insignificant in- 

 jury to them, while the partial drying of sim- 

 ilar cultures will cause them to deteriorate 

 and die rapidly. The time of danger to a 

 drying culture is the time of high concentra- 

 tion of the soluble substances. This condi- 

 tion necessarily obtains when the culture is 

 almost dry. Whether one wishes to base his 

 explanation chiefly upon the antiseptic action 

 of concentrated sugar and salt solutions' or 



'Sternberg, 'Manual of Bacteriology,' 1893, p. 

 156. 



^ John Gelding, Journal of Agricultural Science, 

 Vol. I., Pt. 1, p. 59-64. 



upon the deleterious action of by-products'' 

 which must also be highly concentrated in 

 the almost dry culture, it is necessary to admit 

 that the longer a given culture is exposed to 

 these adverse conditions the fewer bacteria 

 will be able to survive; and as the necessary 

 corollary, the more often a properly dried cul- 

 ture is allowed to become' moist the greater 

 will be the deterioration of that culture. 



This explanation is deduced from the fol- 

 lowing facts: 



1. Cultures of nodule-forming bacteria have 

 been rapidly dried, kept in a desiccator for 

 thirty days, sixty days and ninety days, and 

 revived with no apparent difference in the 

 three series. 



2. Cultures dried as above have been ex- 

 posed to moist air for ten days and for twenty- 

 four days. In some cases contaminations de- 

 stroyed the proper organism; in others com- 

 plete sterility obtained; in a few cases a few 

 organisms remained in cultures otherwise 

 sterile. 



3. Cultures ten days old were evaporated in 

 vaeuo, and into the concentrated broth heavy 

 inoculations were made. These tubes were 

 sterile at the end of seventy-two hours. 



4. Our regular sugar-broth was made up 

 approximately twenty times as concentrated 

 as our regular formula, and this medium was 

 heavily inoculated with actively growing cul- 

 tures. By the end of seventy-two hours these 

 tubes were sterile. 



5. A culture has been placed on cotton, half 

 of which was placed in a sterile petri dish, to 

 make drying very slow, half was dried rapidly 

 and kept over calcium chlorid. After twenty- 

 five days the cotton in the petri dish was 

 sterile; the cotton from the desiccator was a 

 pure culture in good condition, containing 

 numberless organisms. 



We may summarize briefly as follows: 



The nodule-forming bacteria of the Legum- 

 inoseaB may be dried rapidly and kept in a dry 

 condition for long periods," and may then be 

 revived successfully. 



Cultures properly dried may be killed by 

 exposure to moist conditions. 



'See also Bulletin No. 71, Bureau of Plant In- 

 dustry. 



