176 



Biological Therapy 



The injection is generally made in the sub-caudal fold 

 although in some instances the skin of the lower eyelid is 

 used. When the injection is properly made a small pea-like 

 swelling or nodule is immediately apparent, whereas if the 

 tuberculin be injected subcutaneously this swelling is absent. 

 This swelling subsides quickly and is of no diagnostic sig- 

 nificance. A reaction consists of a circumscribed or diffuse 

 swelling at the site of injection twenty-four hours or more 

 after the injection. The following code adopted by the U. S. 

 Livestock Sanitary Association for reading and recording 

 an intradermal reaction will be of assistance and should 

 always be used: 



1. If one observation only is made it shall be at the 



seventy-second hour after injection. 

 If two observations are made they shall be at the 

 forty-eighth and ninety-sixth hours, respect- 

 ively, after injection. Under special conditions 

 more frequent observations over a more ex- 

 tended period of time are advisable. 



2. An intradermic test shall be reported in accordance 



with the following code: 



a. Animals showing no reaction shall be recorded 



at each observation as N — (Negative). 



b. Reactors shall be recorded as follows: 



a. For circumscribed swelling, pea size (diam- 



eter fV") shall be used as a basic 

 standard. Larger swellings shall be re- 

 corded as P-2, P-3, P-4, P-5, etc., in 

 accordance with the findings being two, 

 three, four or five times the size of a pea. 



b. For diffused swellings, ''Thick 2-X" shall be 



used as a basic standard, and signifies 

 a diffuse swelling in which the injected 

 caudal fold is twice as thick as the nor- 

 mal fold. Larger swellings shall be 

 recorded as "Thick 3-X," "Thick 4-X," 

 etc., in accordance with the findings. 



OPHTHALMIC TEST. For this purpose the ophthalmic 

 disc is most generally used. The disc is placed in the con- 

 junctival sac beneath the lower eyelid. It should be held 

 in place for one or two minutes, during which time the disc 



