THE DIAGNOSIS OF TUBERCULOSIS 133 
keeps the space saturated. Ventilation should be restricted to 
a minimum. As a consequence, molds grow luxuriantly, and 
even the gummed labels must be replaced by pieces, of stiff 
manila paper fastened to the tube with a rubber band. By 
keeping the tubes inclined, no undue amount of condensation 
water can collect in the bottom, and the upper portion of the 
serum remains moist. The only precaution to be applied to 
prevent infection with molds is to thoroughly flame the joint 
between tube and cap, as well as the plugged end, before open- 
ing the tube. When test tubes are employed it is well to dip 
the lower end of the plug into sterile molten paraffin and to 
cover the tube with a sterilized paper cap. The white bottle 
caps of the druggist are very serviceable.” 
Unless the tuberculous material is perfectly fresh (uncon- 
taminated) and in the early stages of the disease, it is safer to 
inoculate a guinea pig, and after the lesions begin to develop, 
to chloroform it and make the cultures from the recently 
affected liver or spleen. 
Animal inoculation. The guinea pig is preferable for diag- 
nosis. With tuberculous tissues either of two methods may be 
employed: (1) a piece of the tissue about the size of a pea 
or bean may be inserted under the skin by first making an in- 
cision through the skin and superficial fascia with a sharp scalpel 
and then with a pair of fine forceps, inserting the bit of tissue 
well under the skin and closing the opening with one or more 
sutures ; (2) The tissue may be crushed in a mortar and thor- 
oughly mixed with a few cubic centimeters of sterile water or 
bouillon and then injected with a hypodermic syringe. The 
needle should be of large caliber. If suspected milk is being 
examined it may be injected into the abdominal cavity. If the 
material is tuberculous and contains living tubercle bacteria, 
the death of the animal follows in from 3 weeks to 4 
months. Usually the lymphatic glands of the groin and axilla 
are enlarged and often caseous. If a guinea pig is used, the 
liver, spleen, lungs, and kidneys are liable, in the order named, 
