COMBINED METHOD OF STERILISATION. 117 



"bacteria as are themselves active producers of acid. Benzole acid, 

 though prohibited by law, is occasionally employed for increasing 

 the keeping properties of milk. This acid even in very small 

 quantities has a very restrictive influence on alcoholic fermenta- 

 tion, and it is to this influence that the difficulty of exciting fer- 

 mentation in the juice of the whortleberry ( Vaccinium Vitis 

 Idcea) is to be ascribed, considerable quantities of this acid being 

 present therein, MACH and PORTELE (I.) having found 0.64 to 

 0.86 grm. per litre. 



81. The Combined Method of Sterilisation. 



The influence exerted on micro-organisms by the substances 

 already considered is subject to the same fundamental law as has 

 been established for physical force, viz., that the effect produced 

 varies with the intensity of the causative influence. A solution 

 containing so large a proportion of antiseptic that it is capable of 

 killing a given microbe, will, when sufficiently diluted, have a 

 merely restrictive influence on development, without, however, 

 proving fatal. Proceeding farther in the same direction, a con- 

 dition of dilution will be attained which will exert a favourable 

 effect, stimulating the vital activity of the organism ; and finally, 

 if the degree of dilution be extended beyond this point, no effect 

 will b3 observable. This fact was expressed by HUGO SCHULZ (I.) 

 in the following phrase : " Each impulse exerts on each cell an 

 action whose effect on the activity of the cell is in inverse pro- 

 portion to the intensity of the impulse." A series of researches, 

 which confirm this law, have been made on microbe poisons, but 

 it will be sufficient to simply mention two examples, viz., that of 

 On. RICHET (L), treating of the bacteria of laotic fermentation, and 

 that of BIERNACKI (I.), which deals with alcoholic fermentation. 



This law forms the basis of the theory of toxic action origi- 

 nated by 0. Low (II.) in a book the perusal of which is commended 

 to the reader, and more especially for the complete critical digest 

 it contains of the literature, relating to the action of poisons, pub- 

 lished anterior to 1893. According to Low, the ultimate cause of 

 toxicity is to be sought in the lability of the albuminoid matter 

 of the cell protoplasm. The activity of the latter consists in a 

 continuous chemical change of the atomic groups composing the 

 molecule, the briskness of which alteration is increased by slight 

 stimuli. Larger quantities of the irritant (poison) exert such a 

 strong preponderating influence on the change, that the lability 

 of the plasmic albuminoid is arrested and the life of the cell is 

 consequently destroyed. Probably, then, toxic action may be the 

 means of throwing light upon the obscure problem of the chemical 

 dynamics of the cell ; just as, in many other branches of natural 

 philosophy, the study of disturbing influences has afforded the 

 deepest insight into the normal course of phenomena. 



