280 PUBLIC HEALTH BACTERIOLOGY 



brown, syrupy liquid, containing the products of growth 

 in the culture medium and a 50 per cent extract of the 

 bodies of the bacilli by glycerin ; all in so far as these are 

 indestructible by heat. Stored in a cool dark place it 

 keeps indefinitely, the glycerin acting as a preservative. 

 The dose of this preparation used in cattle is 0-25 c.c., but 

 the stock is usually diluted with 0-5 per cent carbolic water 

 four times, making the dose 2 c.c. Such a dose in a 

 healthy man causes in three to four hours malaise, tendency 

 to cough, laboured breathing, and moderate pyrexia, all 

 passing off in twenty-four hours. In a man suffering 

 from tuberculosis, such a dose would give rise to such an 

 excessive reaction as probably to cause death. Even 

 o-oi c.c. causes all the above symptoms in an aggravated 

 degree, together with marked inflammatory reaction 

 around any tuberculous focus, resulting in necrosis but 

 not killing the bacilli. This is now known as the " tuber- 

 culin reaction," and is much used in veterinary practice. 

 It is also used in clinical work for help in diagnosis of obscure 

 affections suspected to be tuberculous. 



i. Subcutaneously : Use diluted tuberculin, i-iooo, so 

 that i c.c. = i mgr. of tuberculin. Koch in 1890 used 

 I mgr., but now most clinicians begin with o-i mgr. or 

 0-2 mgr. If no reaction occurs, after three to four days 

 give i mgr. If again no reaction follows, wait three to 

 four days and try 5 mgr., and finally, if still negative, 

 10 mgr., but no more. If still no reaction, the person may 

 be considered tubercle-free. Take temperature regularly 

 before and after test. 



ii. Cutaneous test (von Pirquet, 1907). For this test 

 von Pirquet first suggested a 25 per cent solution of " old 

 tuberculin," but the latter is now used undiluted. The 

 patient's skin on the flexor surface of the forearm is 

 sterilized. Two separate drops of the tuberculin are placed 

 on the skin, 2 to 4 in. apart. With a small metal bore 

 the skin is scarified at a point midway between the two 

 drops, and then that is covered by the drops. Within 

 twenty-four to forty-eight hours in tuberculous patients 

 redness round the points, a papule over the scarified surface, 

 and minute vesicles all appear. The control area shows 

 a slight traumatic redness which soon passes off. In a 



