FIXATION OF COMPLEIMENT 



115 



patient's finger with the tip of the little finger of the 

 right hand holding the test-tube, the thumb and index- 

 finger of the left hand holding and constricting the 

 circulation on the other three sides of the patient's 

 finger (see Fig. 12) . With a little practice, sufficient 



Fig. 12. — Showing authors' method of obtaining blood for complement-fixation 

 reactions. Note the little finger of the right hand holding the test-tube, free to exert 

 intermittent pressure over the radial aspect of the patient's punctured finger, held and 

 constricted on three sides by the enveloping thumb and index-finger of the left hand. 



blood can thus be obtained in a minute or two, and the 

 method does not entail any formidable preparation 

 and obviates the possibility of phlebitis incident to 

 faulty venous puncture. In very young children, suf- 

 ficient blood can quickly be obtained by puncturing 



