f 



324 AGRICULTURAL BACTERIOLOGY. 



through the p.orpus_^}iell, and are thus able to grow readily 

 within the egg, where* they soon cause its decay. A bacterio- 

 logical study of eggs has shown quite a number of different 

 bacteria in perfectly whole eggs, freshly laid, and there seems 

 to be no possible means of completely avoiding them. Even 

 after the shell is deposited and the egg laid, bacteria are capable 

 of entering it. The shell is somewhat porous and it has been 

 proved by experiment that bacteria can pass through the pores. 

 In short," the egg must be looked upon as a highly nutritious 

 food product, in most cases already inoculated with several 

 kinds of bacteria, and a body which is practically sure to 

 undergo decay in the course of time. 



It is, however, possible, by certain devices, to delay or pre- 

 vent the growth of bacteria in the egg. If it chances that the 

 egg is not contaminated at the time of laying, which may be 

 true of some eggs, it may be preserved for a long time by any 

 device that prevents external bacteria from entering through 

 the shell. There is no means of keeping the fresh taste to the 

 e gg s f r this is sure to disappear after a few days, but they 

 may be prevented from actual decay if the egg is covered with 

 an impervious coat which prevents the entrance of bacteria and 

 oxygen. Various devices have been adopted for this purpose, 

 such as the packing of eggs in oats or brine, or covering them 

 with a coat of vaseline, etc. The best method yet devised for 

 this purpose is to immerse the eggs in what is known as water- 

 glass, a material composed of sodium and potassium silicate. 

 This is a very cheap commercial article and is bought in the 

 form of a thick syrup. When one part of this syrup is dis- 

 solved in ten parts of water and is then poured over the eggs 

 in a suitable vessel, it effectually prevents the entrance of bac- 

 teria, and proves to be the most efficient means of preventing 

 the decay of eggs. A single gallon of material thus pre- 

 pared will preserve 50 dozen eggs. With this method many 

 of the eggs may be kept for weeks without decay, but 



