96 



LABORATORY EXERCISES IN BACTERIOLOGY. 



must be kept in mind that it is impossible to subject it to temperatures capable of 

 certainly sterilizing it, and that therefore the utmost precautions must be observed 

 in its collection and distribution to tubes to prevent contamination. The same care 

 is to be exercised in the collection when the older method of solidification and 

 sterilization is to be pursued, as the clear, straw-colored appearance of the product 

 cannot be preserved if it should become necessary to sterilize the substance at a tem- 

 perature above 80 to 90 C. If, however, the white opaque solid (like boiled white 

 of egg) is intended, no particular precaution is essential, as this product may be 

 sterilized without injury in steam in the ordinary fractional manner. Even in such 

 case some care that no decomposition should have taken place before preparation 

 of the medium should be had, lest the natural faint alkalinity of the blood be altered 

 and other important constitutional changes have been induced. Usually no attempt 

 at adjustment of the reaction is made, the natural reaction of the serum being suffi- 

 ciently constant and perhaps in some cases a favorable condition for the growth of 

 bacteria inoculated upon it. 



In conditions permitting care in collection these details should be followed in 



order to preserve the natural asepsis of 

 the blood : A tall, narrow jar, with cover 

 which may be sealed against the entrance 

 of atmospheric contamination, is sterilized 



TnT TRT Tl $ * n a * ar & e autoclave, or by boiling ; or the 



sterilization may be performed by disinfect - 

 ing solution (as of mercuric chloride, or of 

 carbolic and hydrochloric acids), with sub- 

 sequent rinsing with well-boiled water, al- 

 cohol, and finally ether. It will be found 

 convenient if the cover of the jar has had 

 two openings drilled into it, these being 

 closed after sterilization by sterile cotton 

 plugs. A suitable rubber tube, five or six 

 feet in length, and of diameter easily enter- 

 ing one of the openings in the cover of the 

 jar is similarly sterilized and rinsed in well- 

 boiled water and wrapped in a sterile towel 



or other protective until required for use. In one end of this a glass canula should have 

 been fitted for insertion into one of the jugular veins of the animal from which it is 

 expected to obtain the blood. At the abattoir the free end of the rubber tube is slipped 

 into one of the openings of the cover of the jar and fastened so as not to be easily with- 

 drawn, the end attached to the canula being meanwhile kept under cover. When 

 the animal is felled, it should at once be drawn up by the hind-legs until the head 

 swings almost clear of the floor. The head is then dragged to one side and the exposed 

 side of the neck cut. At once the canula, with as little exposure as possible, is slipped 

 into one of the cut veins, and the blood allowed to enter the jar. (If the throat is 

 cut completely, as is usual, the operation becomes unnecessarily bloody and filthy.) 

 As soon as the jar is filled, the tube is withdrawn and the cotton stopper readjusted. 

 If no more blood is to be obtained, the tube is now washed well in a normal salt solution 

 to prevent the clotting of adhering blood upon the surface and in the interior. The 

 full jar is set aside for fifteen or twenty minutes for the clot to form; when this has 

 occurred, a long, stiff piece of wire is sterilized in the flame and inserted into one of 



FIG. 28. SERIES OF TUBES ARRANGED FOR 

 COLLECTION AND SEDIMENTATION OF 

 BLOOD-SERUM. 



