290 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



three days and possibly have an increased secretion of sputum, but 

 is then restored to the same condition as before the examination. 



A positive reaction, of course, only means that the patient has 

 a tubercular focus somewhere in his body, but does not in itself 

 indicate whether this is active or not. This point must be decided 

 by the history, the clinical findings, etc. 



Regarding the constancy of the reaction in cases of proved tuber- 

 culosis, in suspected cases and in supposedly non-tubercular individ- 

 uals the accompanying table will furnish the desired information: 



Pulmonary tuberculosis .... 90.0 to 100.0 per cent. 



Suspected cases 92.1 per cent. 



Non-suspected cases 56 . 1 per cent. 



The high percentage of positive findings in non-suspected cases 

 is readily explained, if we bear in mind how common a latent, 

 inactive tuberculosis actually is. 



As to indications and contraindications it will suffice to state that 

 the test may be made in all suspected cases unless heart lesions, 

 diabetes, nephritis, or pregnancy exist, or unless laryngeal tuber- 

 culosis is suspected. 



To illustrate the general safety of the procedure, providing that 

 the rules of dosage given above are implicitly followed, I 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 exami- 

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



