To disinfect hands and arms. Operating surgeons are those to whom it is a most urgent necessity to cleanse hands and arms antiseptically. Carbolic acid (1–20, or 1–40) is used for this purpose.
It is hardly necessary to add that in a case of infectious disease occurring in a household many of these modes of application, perhaps all of them, must be adopted. Formalin is probably the best gaseous disinfectant which we have, but its use does not, and should not, preclude the simultaneous adoption of other methods.
[APPENDIX]
It is proposed to add one or two notes on certain technical points in bacteriological work, with a view to assisting those medical men not able to obtain the advantages of a well-equipped laboratory, and yet desirous of occasionally attempting some practical bacteriology.
1. General Examination. All fluids may be examined for bacteria in two chief ways:
(a) A small quantity may be placed on a cover-glass or slide, dried over a lamp or bunsen flame, and stained with aniline dyes for a few minutes. It is then ready for microscopic examination. It is obvious that the result will generally be a mixture of bacteria, for which differentiating stains may be used (Gram, Ziehl-Neelsen, etc.).
(b) A minute drop of the suspected fluid may be added to various fluid media (broth, liquefied gelatine, etc.) and then plated out upon small sterilised sheets of glass. In the course of two or three days the contained bacteria will reveal themselves in characteristic colonies, which may be examined, and if possible sub-cultured, and carefully studied.
Double-Staining Methods. These are various, and are used when it is desired to stain the bacteria themselves one colour, and the matrix or ground substance in which they are situated another colour. Three of the commoner methods are those of Ehrlich, Neelsen, and Gram. They are as follows: