314 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



To illustrate the general safety of the procedure, providing that 

 the rules of dosage given above are implicitly followed, we would 

 point out that Lowenstein did not meet with any serious symptoms 

 or a single death in a series of 20,000 single injections which were 

 made under his direction. 



The Tuberculin Test According to v. Pirquet (Cutaneous Method). 

 The inner surface of the forearm is cleansed with ether, then two 

 drops of the concentrated old tuberculin of Koch are placed about 

 10 cm. apart. With a special instrument, which v. Pirquet terms 

 an "Impfbohrer" (vaccination gimlet), and which is essentially 

 an exceedingly fine chisel with a platinum iridium point that can 

 be sterilized in a flame, a small abrasion is first produced midway 

 between the two drops. To this end the instrument is pressed 

 against the skin and rotated, sufficient force being employed to 

 produce a definite abrasion, without, however, causing any bleeding. 

 A similar scarification is then made through each one of the two drops 

 of tuberculin. A tiny bit of sterile absorbent cotton is now laid 

 across each drop so as to prevent it from flowing away. After five 

 minutes this is removed. A dressing is not used. Should examina- 

 tion at the expiration of twenty-four to forty-eight hours not reveal 

 the existence of a distinct brown scab measuring about 1 mm. in 

 diameter, both at the point of inoculation as well as at that of con- 

 trol, the abrasion has been too slight, and the test must be repeated. 



The appearance of a positive reaction when fully developed is 

 well shown in Plate VII, and contrasts markedly with that of the 

 control. If the abrasions are examined at frequent intervals it will 

 be observed that a small wheal appears within a few minutes both 

 -at the control and the test point which soon becomes surrounded 

 by a pink halo. This disappears after a few hours, leaving a small 

 red area, in the centre of which a tiny scab begins to form. At 

 the control point the redness is still discernible after twenty-four 

 hours, but then fades away. At the test-point, in positive cases, 

 the red area begins to increase in size after a period of time which 

 varies between three hours and several days. Coincidently the 

 inflammatory area becomes elevated (papular) and develops rapidly 

 in size. At the end of forty-eight hours the reaction has usually 

 reached its height. At this time the diameter of the "papule" will 

 average about 10 mm., but it may be much larger up to 30 mm., 

 the size, cceteris paribus, depending upon the quantity of tuberculin 



