144 BACTERIOLOGY. 
How are animals inoculated artificially ? 
Through the capillary circulation of the skin or by hypodermic injec- 
tions, either subcutaneous, intra-venous, or into some of the larger 
cavities of the body. 
What precautions should be observed in handling materials that 
are to be examined for bacterial infection ? 
All fluids should be received in sterilized flasks, and all solids 
should be wrapped in sterilized cloths that have been moistened with 
a 1 to 1000 corrosive sublimate solution. 
What conditions are necessary for growing bacteria artificially ? 
A suitable temperature and the proper amount of moisture, together 
with some organic material containing nitrogen and carbon. As arule 
the nutrient mass must be neutral or slightly alkaline in reaction. 
What kind of media were first used in cultivating bactéria ? 
Artificial fluid media were made containing proper nutriment mate- 
rial, as grape sugar, ete. It was seen, however, that bacteria grew 
better under conditions more closely resembling their natural state. 
Therefore, infusions of meat were prepared which held sufficient albu- 
minous nutriment material in solution. The trouble with these fluid 
media is that with them it is very difficult to separate _—_ different 
varieties of bacteria one from the other. 
What media are now most often used ? 
Solid media; either pieces of sterilized potato or those having an 
animal or vegetable gelatin for a base. 
What fluid media are now employed ? 
Infusion of hay and other vegetable substances are used for growing 
bacteria which are purely saprophytic. While for those forms that are 
parasitic beef bouillon is used. 
How is the beef bouillon prepared ? 
Take 500 grams of finely chopped beef, as lean as possible, and add 
1 litre of water. Allow it to stand twelve hours. If in summer it 
must be kept in a refrigerator. Then turn the whole 1500 grams of 
material into a cheese-cloth strainer and squeeze out just 1000 grams of 
fluid. To this is added 10 grams of peptone and 5 grams of common 
table salt. The mixture is then boiled about three quarters of an hour 
in a water bath. The liquid is usually strongly acid, and is neutralized 
by the cautious addition of a saturated watery solution of sodium carbon- 
ate. Again the fluid is boiled for about an hour and the coagulable 
