252 MICROBES, FERMENTS, AND MOULDS. 
to ensure the destruction of all germs. A very small 
aperture is left at the top of the case 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, ete., 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 
desiceation, 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 
free 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 
