THE WASSERMANN REACTION 615 



[Although 0-5 c.c. of blood will suffice, it is preferable to have 

 more, 1 c.c. ; this is easily obtained by the method described. 

 Many withdraw the blood from a vein by puncture with a hollow 

 needle.] 



Cerebro-spinal fluid is obtained by lumbar puncture ; it should 

 be free from blood. 



II. APPARATUS AND MATERIALS REQUIRED FOR THE TEST. 

 (a) Copper racks, each to hold 24 test-tubes (size as in (b) ). 



(b) Test-tubes, 4 in. x f in. These should be carefully cleaned 

 and finally rinsed in distilled water, drained and dried. 



(c) Graduated pipettes, etc. : 0-1 c.c. in tenths (= 0-01 c.c.), 

 1 c.c. and 10 c.c., long form graduated to the point. For measure- 

 ments above 10 c.c., graduated stoppered cylinders are used, 

 50 c.c. and 100 c.c. 



(d) An inactivating water-bath with regulator. The bath is 

 set for a temperature of 56-57 C. A good form of bath is made 

 by Messrs. Hearson, which may also be employed for sterilising 

 vaccines at 65 C. 



(e) For incubation, the ordinary warm (37 C.) incubator may 

 be employed. [A water-bath at 37 C. may be used, and special 

 forms heated by gas or electricity are made by Messrs. Hearson. 

 Incubation in a water-bath reduces the period of incubation to 

 one-half that required in an air incubator.] 



(/) Saline solution. A solution of 0-85 per cent, sodium 

 chloride in distilled water ; it should be freshly prepared on each 

 occasion. 



(g) Washed sheep's corpuscles. Collect the blood from a freshly 

 killed animal into a stoppered bottle containing a few pieces of 

 glass rod and iron wire. Fill only half full. Shake continuously 

 for sufficiently long to defibrinate it. The blood will keep in the 

 ice chest for three or four days. When required, fill the glass 

 centrifuge buckets with the blood and drive down the corpuscles. 

 Remove serum and add saline ; shake and centrifuge. This con- 

 stitutes the first washing. There must be three washings in all. 

 The first may be carried out the day before the corpuscles are 

 required. After the third washing remove the saline without 

 shaking up the corpuscles. 



(h) Guinea-pig complement. On the day of the test kill a 

 guinea-pig by cutting its throat and collecting the blood in a, 

 saucer. The animal is first stunned slightly by knocking its head 



