DIAGNOSTIC REACTIONS 297 



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

 can be obtained by puncturing the heart with an antitoxin syringe, 

 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 totally 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 1J to 2 inches long, and having an inside 

 diameter of J 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.; after this it is 

 diluted 1 in 5, and is then ready for use. 1 



A normal serum and a specimen from a known case of syphilis 

 should always be available as controls. 



It is recommended that all sera should be examined on the day on 

 which they have been procured. This no doubt is a good rule, but 

 I have found that fixing sera remain active for several weeks. It is 

 thus perfectly feasible to send specimens from a distance, especially 

 if the serum is separated from the corpuscles after bleeding the 

 patient. 



As human serum frequently contains amboceptors which are 

 hemolytic for sheep corpuscles in the presence of complement, and 

 as their amount is variable and at times not inconsiderable, a factor 

 is here introduced into the experiment which could convert a positive 

 into a negative result. For we must bear in mind thaf the activity 

 of amboceptor and complement stand in an inverse proportion to 

 one another, such that a very small amount of complement would 



1 If it should be desired to secure somewhat larger amounts of blood by vene- 

 puncture, the vacuum bulb recommended by Keidel will be found very convenient 

 (see Jour. Amer. Med. Assoc., May 25, 1912, p. 1579). 



