166 OUTLINES OF BACTERIOLOGY 



water. This may seem a very large percentage, but in comparison 

 with other organisms, it is not an inordinate amount. Thus, human 

 beings consist of 65-70 per cent., vegetables of 60-80 per cent., and 

 algae of about 90 per cent, of water. It is small wonder, therefore, 

 that drying should have such a marked effect upon the keeping 

 qualities of various foods. This method is very old, and is the one 

 most extensively employed, Thus, in the preparation of hay, the 

 newly cut grass is left to dry, for the farmer is well aware that no 

 putrefactive change can take place while the grass is in a dry state. 

 In the case of flesh-foods drying is more difficult, because the process 

 takes a long time, and during this period, in most countries, putre- 

 faction would intervene before the process had been completed. In 

 countries where the air is dry this process is quite feasible ; thus, during 

 the South African War, some of the raw flesh was prevented from 

 putrefying for some time by direct exposure to the atmosphere ; when 

 thus exposed to the air no putrefaction set in. Many tribes of savages 

 preserve meat by cutting it into thin strips and hanging it out in the 

 sun to dry. The food called pemmican consists of meat cut into thin 

 slices, divested of fat, and dried in the sun. After drying it is 

 pounded, and then mixed with fat, dried fruit, etc. Pemmican will 

 keep for a long time, and does not occupy much space. 



The drying of flesh may be accomplished in another way, viz. by 

 smoking. In this country smoking is carried on to a considerable 

 extent. It must be noted that it is the drying and not the smoking 

 that prevents bacteria and other organisms from gaining a footing, for 

 though smoke is a slight antiseptic it is not powerful enough to prevent 

 bacterial growth. In some places the smoke is obtained by the burning 

 of certain woods, which contain antiseptic substances, like creosote and 

 phenol. The evaporation of such substances add their quota to the 

 injurious influences brought to bear on the bacteria. 



The drying of fruits is at once a simple and an efficacious method of 

 preservation, but many kinds of fruits, e.g. tomatoes, would be ruined 

 during the process, so that drying is of no use in their case. Among 

 others we may mention pears, apples, grapes, currants, raspberries, 

 blackberries, figs, and dates, as fruits which readily lend themselves to 

 preservation by the drying method. It is well to bear in mind that 

 drying does not destroy the microorganisms on the fruit, and it is 

 only necessary to moisten the fruit and lay it aside for a day or 

 two to observe putrefaction setting in : in a very short time the 

 surface of the fruit will be covered with an extensive growth, usually 

 of moulds, sometimes of other organisms. Of recent years, drying 



