August 21, 1908] 



SCIENCE 



237 



whicli will allow the fungus thallus to make 

 a good growth, but prevent it from forming 

 organs of fructification ; this is the antigenetic 

 concentration. The antibiotic concentration 

 is one sufficient to kill an adolescent thallus; 

 however, two sorts of antibiotic effects are 

 exhibited by thallophytes when acted upon by 

 poisons. (1) Before reaching the fatal con- 

 centration, a point is found at which the plant 

 ceases to grow. This point is designated the 

 partial antibiotic concentration, and may be 

 represented by an action analogous to that of 

 ether or chloroform, which deadens or sup- 

 presses some of the functions. (2) The total 

 antibiotic concentration causes a sudden and 

 complete termination of the vital functions. 



In estimating the effect of toxic solutions 

 in his investigation, LeEenard made use of a 

 new standard. On account of the very dilute 

 solutions sometimes used, the fungus could 

 make bvit little growth and the usual criterion 

 of dry weight was inapplicable. He, there- 

 fore, determined what was practically the 

 antiairxic concentration in each case. This 

 was determined by ascertaining the point at 

 which the majority of spores became vacuo- 

 late, transparent, and with some swelling 

 assumed a spherical or elliptical form, i. e., 

 utricular germination. Such a spore, if 

 transferred to a nutrient solution, will germ- 

 inate and develop a normal thallus; but left 

 in the antiauxic solution, it develops no fur- 

 ther than the germ-tube stage. 



The complete nutrient solution used con- 

 tained C,H,A+NH,N03-|-MgS0,-|-KH,P0. 

 +H2O. The experiments consisted in de- 

 termining the maximum concentrations of 

 four salts of copper (the acetate, chloride, 

 nitrate and sulphate) which would allow the 

 utricular germination in the presence of a 

 complete or incomplete nutrient. The results 

 obtained may be briefly summarized as fol- 

 lows: 



Neither single mineral salts in solution 

 weaker than the normal, nor organic com- 

 pounds containing no acid or metal radicals, 

 have any antitoxic value against copper salts 

 for Penicillium glaucum; but the salts of 

 K, Mg, NHj, or organic acids which contain 

 in their structure the groups CH3, CH., or CH 



singly joined to a functional acid group pos- 

 sess an antitoxic value. 



The bases combined with active organic 

 acids determine the relative antitoxic value 

 of the salts of these acids. 



The amine group NH^ destroys the anti- 

 toxic value of CH^. The imide function, 

 OCE", is more or less indifferent. The nitrile 

 group, CN, is distinctly toxic. The organic 

 combinations of C and of N taken singly 

 are therefore inactive. 



Carbohydrates, when added to an appro- 

 priate mineral salt, exhibit an antitoxic value, 

 which for a constant quantity of appropriate 

 salt vanishes at about the centinormal con- 

 centration with aldoses; but goes somewhat 

 higher for ketoses and complex hexoses. The 

 aldehyde and ketone functions play, therefore, 

 a very important function in the antitoxic 

 action of these bodies. The position of the 

 hydrosyl groups in the carbohydrates has very 

 little influence upon the antitoxic value. 



The appearance of antitoxic action is de- 

 pendent upon the simultaneous presence of a 

 combined carbon compound, and of a suitable 

 mineral salt forming an organo-metallic com- 

 pound, which recalls by its formation and 

 modifications the side-chain of Ehrlich. 



The antitoxic value of the carbon group in 

 a mixture varies with the quantity of metal 

 or of mineral salt united to this carbon group. 



The dissociation of the mineral salts in- 

 duces a sudden decrease in their antitoxic 

 value, and the molecules of the useful salts 

 (organic or inorganic combined with carbon 

 compounds) generally appear more active 

 than the ions for the K and Mg salts and 

 also for certain salts of NH,. The effect of 

 the ions is generally independent of their 

 quantity. Sometimes their effect diminishes 

 proportionally to their quantity, but generally 

 there must be a material diminution in quan- 

 tity before any effect can be noticed. 



Certain salts exhibit specific properties. 

 The antitoxic value of the NO3 ions becomes 

 zero when the total quantity of NO3 in solu- 

 tion becomes equal to or less than 0.000352 

 per cent. SO, shows the same phenomenon 

 when the quantity becomes 0.000096 per cent. 

 In the presence of an excess of K, the ions 



