74 BACTERIA IN RELATION TO PLANT DISEASES. 



organism is placed in a flask or large tube. That for the other organism is placed 

 inside a Chamberland filter, which is then sunk into the other receptacle, whereupon 

 it is sterilized and inoculated as in the collodion-sac method. 



The favorable influence of a second organism may be studied in crossed streaks 

 on sterile raw potato, carrot, turnip, etc.; on starch jelly ; or on agar, gelatin, or 

 silicate jelly with addition of varying amounts of the different plant acids, or plant 

 juices, or other vegetable substances. Frost's divided Petri dish may be used for 

 the jellies. 



REACTION TO ANTISEPTICS AND GERMICIDES. 



Antiseptic has been defined recently by Duclaux as follows : Any substance 

 the intervention of which modifies in any form whatsoever the march of the phe- 

 nomena (Bibliog., XX, Fermentation alcoolique, p. 461). 



I still use the word with its old primary meaning (anti, against, and sepsis, 

 decay). In this sense an antiseptic is any substance which prevents the multi- 

 plication of bacteria in putrescible substances. Large doses of antiseptics often 

 exert a germicidal action, but such action does not necessarily follow. Often when 

 the antiseptic substance is removed or diluted beyond a certain point growth takes 

 place. The first seven substances mentioned below possess very active germicidal 

 powers and are antiseptic in correspondingly small doses ; the remainder are more 

 or less valuable antiseptics, but are not valuable germicides. 



(i.) Mercuric chloride. (5.) Lysol. ( 9.) Benzoic acid. 



(2.) Sulphate of copper. (6.) Trikresol. (10.) Salicylic acid. 



(3.) Formaldehyd (formalin). (7.) Methyl violet (Pyoktanin). (11.) Chloroform. 



(4.) Phenol (carbolic acid). (8.) Thymol. (12.) Sulphuric ether. 



This list may be extended indefinitely. The student should consult valuable 

 digests in Sternberg's Text Book of Bacteriology and in Miquel & Cambier's Traite 

 de Bacte'riologie. Some caution must be used in drawing conclusions from experi- 

 ments. Mercuric chloride does not always destroy when the culture medium 

 contains albuminoid substances. Sulphate of copper is more active in water than 

 in bouillon.* Some organisms will grow in a solution saturated with thymol (e.g., 

 in bouillon). Others will grow in the presence of chloroform (5 cc. of chloroform in 

 test-tubes with 10 cc. of milk or beef-bouillon). Ten organisms have been found by 

 the writer which, under the conditions named, grew in the presence of chloroform 

 and two which grew vigorously in the presence of thymol. Russell reports one 

 capable of growing in the presence of sulphuric ether. It is, therefore, not always 

 safe to depend on these substances as antiseptics. Newcombe has made the same 

 observation (Cellulose Enzymes, Annals of Botany, Vol. XIII, 1899, p. 60). In the 

 opinion of the writer the statements of physiologists respecting the existence of 

 enzymes in the tissues and fluids of the higher plants and animals must be taken 

 with much allowance when chloroform, thymol, and similar antiseptics have been 



*Moore, George T., and Kellerman, Karl F. A Method of Destroying or Preventing the Growth 

 of Algae and Certain Pathogenic Bacteria in Water Supplies. U. S. Department of Agriculture. 

 Bureau of Plant Industry, Bulletin 64, 1904, pp. 44; see also Bull. 76, Bureau of Plant Industry. 

 Certain pathogenic bacteria, such as Vibrio cholerae and Bacillus typhosus, are destroyed within a 

 few hours in water containing traces of copper salts or dissolved particles of metallic copper. 



