298 MEDICAL BACTERIOLOGY 



top and held in position by means of a surgeon's knot, loosely drawn. 

 The cord should be quite stout so that the sac can later be tightly 

 closed. The ends of the cord are brought outside of the tube as 

 shown at B, Fig. 34, 2. Sterilization may be accomplished either in 

 the autoclave or by means of the intermittent method of sterilization. 



The medium is inoculated by means of the platinum needles in 

 exactly the same way in which tube cultures are ordinarily inocu- 

 lated. The sac thus inoculated should be incubated for twenty- 

 four hours and if the medium outside of the sac remains clear the sac 

 may be used. Otherwise it would be discarded. 



The tube is placed in a tumbler or test-tube rack. The sac is 

 then pulled out of the tube until the cords can be drawn tight so as 

 to close the sac and securely tied. With sterile scissors the end of 

 the sac is cut off a few millimeters above the constriction. . If there 

 is any moisture on the inside of the sac above the neck this must be 

 removed with sterile filter paper and then a few drops of a thin 

 solution of collodion is placed in the neck so as to hermetically seal 

 the sac. The long and contaminated ends of the cord are now cut 

 off, the sac dropped back into the test-tube, and the cotton stopper 

 replaced. (Fig. 34, 3.) The sac is now ready to be placed in the 

 body cavity of an animal. (Frost.) 



The method of inoculation is especially useful in increasing the- 

 virulence of attenuated forms, and in producing immunity in ani- 

 mals to induce the agglutinating and lysogenic properties in the 

 blood. 



References. Harris, C. f . B. I., 1902, 32 : 74 ; Frost, Proc. Am. 

 Pub. H. A., 1903, 28, p. 536. 



Intravenous A rabbit is generally chosen for this purpose and 

 the inoculation made into an ear vein. Of the three branches of 

 the vena auricularis posterior, the ramus lateralis posterior is the 

 smallest, but, due to the fact that it is the most firmly imbedded in 

 connective tissue, it is much more easily entered than the others. 

 The artery forceps (Fig. 

 35, a) are used to gorge- the 

 vessel and are, of course, 

 removed before the mate- 

 rial is injected. Avoid the 

 introduction of air, which 

 causes immediate death, 

 and keep the animals up- 

 der close observation for 



Pig. 35. Dorsal view of right ear of rabbit. 

 one hour. », artery forceps; 6, syringe. 



