THE DESTRUCTION OF BACTERIA . 87 



Sputum is a substance extremely difficult to disinfect because the 

 bacteria present are surrounded by dense envelopes of mucus, through 

 which disinfectants do not easily diffuse. For sputum disinfection, es- 

 pecially tuberculous sputum, carbolic acid 5 per cent solution or 

 any of the phenol derivatives in similar concentration, may be used. 

 Bichloride of mercury is of very little use in sputum disinfection be- 

 cause of the dense protective layers of albuminated mercury which form 

 about the microorganisms. Sputum should always be received into 

 cups containing the disinfectant, and contaminated handkerchiefs 

 should be soaked in the solution. 



Feces from typhoid, dysentery, and cholera patients should be steril- 

 ized by burning, if possible, or by thoroughly mixing with large quan- 

 tities of boiling water; but if chemical disinfectants are to be used, five 

 per cent carbolic acid or dilute formalin are convenient. Milk of lime 

 and chloride of lime are useful, though somewhat inconvenient. Bichlo- 

 ride of mercury is of little value in this case for the same reason 

 that it is valueless in sputum disinfection. In all cases of feces dis- 

 infection it is extremely important that the chemical agent should be 

 added in large quantities and thoroughly mixed with the discharge. 



Linen, napkins, and other cloth materials which have come into con- 

 lact with patients should be soaked for one or two hours in one per cent 

 formaldehyde, five per cent carbolic acid, or 1 : 5,000 or 1 : 10,000 

 bichloride of mercury. After this, the material may be taken from the 

 sick-room and boiled. It is extremely important that cloth material 

 should never be removed from the sick-room in a dry state. 



Urine may be easily disinfected by the addition in proper con- 

 centration of any of the disinfectants named above. 



The methods for sterilization of surgical instruments and the prepara- 

 tion of the skin of the patient for operation are subject to so many local 

 variations that it is hardly within the scope of a text-book on bacteriology 

 to mention them. Metal instruments are usually sterilized by boiling 

 in soda solution and may be subsequently immersed in five per cent car- 

 bolic acid solution. Catgut may be sterilized by boiling in alcohol or by 

 subjecting it to temperatures of 140 C. and over, for several hours in 

 oils (albolin). 



The disinfection of the hands is also a matter of much variation. 

 Two methods frequently quoted are those of Welch and of Fiirbringer. 



In Welch's method the hands are brushed with green soap in water 

 as hot as it can be borne for at least five minutes. They are then rinsed 

 and immersed for two minutes in a warm saturated solution of perman- 



