160 BACTERIA. 



Gases. — Hydrogen and carbonic acid are believed to stop 

 movement of the motile bacteria. Chloroform is believed to 

 arrest the changes brought about by the zymogenetic species. 



Electricity. — Cohn and Mendelssohn found that a constant 

 galvanic current produced a deleterious effect owing to electrolysis. 



Light. — Sunlight is fatal to putrefactive bacteria. 



Carbonic Acid. — A 5% will kill the spores of B. anthracis 

 in 24 hours. 3% will not do so in the same time. A i % kills the 

 bacilli. 



Chloride of Zinc in 5% has no effect on anthrax spores, 

 even when they have lain in it for a month. 



Sulphurous Acid is not a good disinfectant, and will not 

 penetrate compact masses or bundles. 



Corrosive Sublimate has the most powerful effect on the 

 organisms, an aqueous solution of i : 20,000 kills the spores of 

 bacilli in 10 minutes. A solution of 1 : 5,000 is thus a certain 

 disinfectant. 



Iodine, Bromine, and Chlorine, are far more active than sul- 

 phurous acid. Bacilli cease to grow in Iodine of i : 5,000, and 

 of Bromine of i : 1,500. 



The Oils of Thymol, cloves, peppermint, mustard, turpentine, 



eucalyptus, all restrain their development ; the latter being 



very good, and is especially useful in Dental cases to prevent 



bacterial growth in the teeth, as it penetrates the tubules. All 



disinfecting reagents should be used in aqueous 



solutions. 



Practical Work. 



(i) Observe Brownian movement in gamboge, etc., suspended 



in water. 



(2) Turbid hay infusion under high power. 



(3) Stain the various organisms. 



(4) Stain with magenta. 



(5) Observe cilia in Spirillu?n, 



To Stain the Bacteria. — The following methods are useful for 

 all Bacteria, Micrococci, and Bacilli, except those of Tubercle and 

 Leprosy : — Dry a film of fluid containing the Bacteria on a cover- 



