252 MICROBES, FERMENTS, AND MOULDS. 



to ensure the destruction of all germs. A very small 

 aperture is left at the top of the ease for the escape 

 of steam and air, which is closed with a drop of solder 

 before the ebullition of the liquid within is completely 

 over. 



The envelopment of meat in its own fat, its pre- 

 servation in sugar, wax, etc., are analogous protective 

 processes, always employed at a high temperature. 



When meat is smoked, the aromatic principles of 

 carbolic acid, creosote, etc., contained in the smoke, 

 destroy the ferments and prevent the subsequent 

 development of air-germs. It is, therefore, a true anti- 

 septic, analogous to the salts used to preserve meat 

 or fish by pickling. Meat may also be preserved by 

 desiccation, when it is cut in thin strips and exposed 

 to the sun and air. This constitutes the jerked beef 

 of South America. 



Excellent results are now obtained by drying meat 

 at from 35 to 55 in a stove through which a current 

 of dry air is passed. The powdered meats to be ob- 

 tained from chemists, which are of great use in nourish- 

 ing the sick and convalescent, are prepared by an 

 improvement on this process. They are absolutely 

 freo from smell, and will keep as long as they are 

 protected from damp. Vegetables cooked by steam, 

 and then compressed and dried, may be kept for 

 several years. 



Refrigeration by ice has been used to preserve 

 meat. But when congelation has occurred in the 



