THE ACTION OF ANTISEPTICS 175 



other organisms, however, such as the paratyphoid bacillus, 

 the presence in a culture especially in a young culture of 

 highly resistant forms renders the initial action of an antiseptic 

 less marked. The action of an antiseptic, like the action of an 

 acid and an alkali, is very much increased by raising the 

 temperature ; from which follows the practical conclusion that, 

 in any disinfection, the use of warm solutions is advisable. 

 Chick and C. J. Martin have further investigated the fact that 

 the presence of albuminous material in a mixture of disinfectant 

 and bacteria decreases the action of the disinfectant, and 

 consider that the latter is adsorbed by the albumin. They have 

 shown grounds for believing that a disinfectant in an emulsion- 

 ised form is more efficient than a similar disinfectant in actual 

 solution, because of a similar phenomenon occurring; for, 

 just as a disinfectant may be put out of action by being 

 adsorbed by organic particles, so when these organic particles 

 happen to be bacteria, the adsorption process causes a greater 

 concentration of the antiseptic round the bacterial protoplasm, 

 and thus hastens its death. 



Though nearly every substance which is not a food to the 

 animal or vegetable body is more or less harmful to bacterial 

 life, yet certain bodies have a more marked action than others. 

 Thus it may be said that the most important antiseptics are the 

 salts of the heavy metals, certain acids, especially mineral acids, 

 certain oxidising and reducing agents, a great variety of sub- 

 stances belonging to the aromatic series, and volatile oils generally. 

 In comparing different bodies belonging to any one of these 

 groups the chemical composition or constitution is very important, 

 and if such comparisons are to be made, the solutions compared 

 must be equimolecular in other words, the action of a molecule 

 of one body must be compared with the action of a molecule of 

 another body. This can be done by dissolving the molecular 

 weight in grammes in, say, a litre of water (see p. 34). When 

 this is done, important facts emerge. Thus, generally speaking, 

 the compounds of a metal of high atomic weight are more 

 powerful antiseptics than those of one belonging to the same 

 series, but of a lower atomic weight. Among organic bodies, 

 again, substances with high molecular weight are more powerful 

 than those of low molecular weight thus butyric alcohol is more 

 powerful than ethylic alcohol and important differences among 

 the aromatic bodies are associated with their chemical constitu- 

 tion. Thus among the cresols the ortho- and para-bodies re- 

 semble each other in general chemical properties, and stand apart 

 from metacresol ; they also are similar in antiseptic action, and 



