TOXINS / 749 



0.25 C.C., of old tuberculin. If tuberculin is to be kept for any 

 period, it is better to procure the concentrated toxin and dilute 

 it with a Yz per cent, carbolic acid solution prior to injection. 

 In old and emaciated animals double the ordinary dose of tuber- 

 culin should be used, and in re-tests three times the usual dose 

 of tuberculin should be injected. Tuberculin should be kept in 

 a cool, dark place and should be rejected if it becomes cloudy.' 

 The dosage is adjusted somewhat to the weight of the animal. 

 Yearlings and 2-year-olds may be given 1 to 1.5 c.c. Bulls and 

 large animals may receive 3 c.c. 



Ophthalmo-Tuberculin Diagnostic Test. — Simultaneously 

 both Calmette of Lille and Wolff-Eisner of Berlin announced 

 this test in June, 1907. It consists in dropping one drop of a 

 1 per cent, solution of tuberculin in the' eye. In tuberculous 

 subjects this is followed by hyperemia, lachrimation, and redness 

 of the eyelids, which begins in about 3 to 8 hours, reaches the 

 maximum in 8 to 14 hours, and remains 1 to 4 days. There is 

 often edema of the lids and purulent discharge. The reaction is 

 caused by an acquired resistance to the disease as shown by local 

 leucocytosis and hyperemia. ISTo harm results to the normal eye. 



The solution is made by precipitating crude tuberculin with 

 alcohol, the precipitate is collected and dried and dissolved in 

 normal salt solution. 



Both recent lesions, and those entirely healed in healthy 

 subjects, will give a positive reaction to the ophthalmo-tuberculin 

 test. 'Wolff-Eisner claims that a positive eye test shows only 

 active lesions. This is not substantiated. The eye test is posi- 

 tive in 18.5% of apparently healthy subjects and is negative in 

 some 20% to 30% of active and healed lesions known to be 

 tuberculous. It is best to perform the test early in the morning 

 to observe the results. One should hold down the eyelid in mak- 

 ing the instillation and gently massage the lids afterwards. If 

 the ocular test proves negative on its first trial it may be re- 

 peated in the other eye after the lapse of three days. It should 

 not be repeated much later than this, or one may get a reaction 

 in the eye of any healthy animal owing to sensitization of the 

 subject (anaphylaxis). _ _ 



Tablets for dilution (and glass tubes containing single 

 doses) of tuberculin for the eye reaction may now be bought of 

 makers of biological products— together with pipette and di- 

 rections for using. ,,-,., -a j.- s 



The skin reaction to tuberculin, rubbed into scarihcations o± 

 the epidermis, has also been used as a test for the presence of 



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