REACTIONS DEPENDING UPON COMPLEMENT FIXATION 311 



the leukocytes. It is accordingly perfectly admissible to kill the 

 animal on the morning of the experiment. In order to obtain as 

 large an amount of serum as possible it is advantageous to let the 

 blood stand for a few hours before it is finally centrifuged. Before 

 use the serum is diluted 1 in 10. The unused portion of the con- 

 centrated serum may be kept frozen, for one or two days, but before 

 further use it must be tested and adjusted to the hemolytic ambo- 

 ceptor as described. Very often it will be found to be inert. In my 

 laboratory, we have set aside special days of the week for comple- 

 ment-fixation work, and we then make no attempt to preserve any 

 of the complement. 



Where only a few specimens are to be examined at one time it 

 is not necessary to kill the animal. A few cubic centimeters of blood 

 can be obtained by puncturing the heart with a syringe or a Keidel 

 tube under anesthesia. My own preference, however, is to kill the 

 animal. 



As has already been indicated, the complement, before use, 

 whether fresh or not, must always be adjusted to the amboceptor. 



5. The Patient's Serum. It is generally recommended to secure 

 blood from the patient as well as from the normal controls by vene- 

 puncture. This, however, is unnecessary. The required amount 

 can be readily obtained from the ear. This is punctured with a 

 small lancet or tenotomy knife, introducing the blade, at an angle, 

 into the lobule and making a small sweep of the point of the blade 

 without enlarging the skin incision, so as to cut a larger number 

 of capillaries. Enough blood can then be milked out in about five 

 minutes to fill a glass tube 1^ to 2 inches long, and having an inside 

 diameter of | of an inch. The tube is corked and thus brought 

 to the laboratory. The clot is then separated from the walls and 

 the corpuscles packed down by centrifugation. The supernatant 

 serum is pipetted off with Wright pipettes, placed in tubes similar 

 to those in which the blood is collected and inactivated (complement 

 destruction) by heating for thirty minutes at 56 C. 



Larger quantities of blood (4 to 5 c.c.) are most conveniently 

 obtained by the aid of the Keidel tube. As shown in the accom- 

 panying illustration this is essentially a bulbed tube which is drawn 

 out to a fine point, exhausted of air with a vacuum pump and sealed. 

 A rubber tube connects the bulb with a hypodermic needle which 

 is provided with the usual stylet. The needle as well as the rubber 



