306 A MANUAL OF BACTERIOLOGY 



improvement results, so much so that a cure is apparently 

 effected ; but, unfortunately, when the treatment is 

 discontinued the scar usually breaks down and the disease 

 returns. Nevertheless, a few cases have remained perma- 

 nently healed. 



For treatment, the dose to commence with should not 

 be more than O0001 c.c., dilutions being made with O5 

 per cent, carbolic solution, and the dose is repeated when 

 all reaction has passed away and is gradually increased. 

 Tuberculin R, or tuberculin BE, is now generally employed 

 (see below). 



Healthy guinea-pigs bear considerable injections of 

 tuberculin without harm ; but if they be tuberculous, if 

 the disease is advanced (eight to ten weeks after inocula- 

 tion), doses of O01 c.c. produce death ; if less advanced 

 (four to five weeks after inoculation) a larger dose, O2 

 to O3 c.c., is required ; but O5 c.c. always proves fatal. 

 The post-mortem appearances are congestion of the 

 lymphatics and viscera, and dark red spots, from mere 

 points to the size of a hemp-seed, on the liver and spleen. 

 These are due to enormous engorgement of the capillaries 

 in the immediate neighbourhood of tuberculous deposits, 

 actual extravasations of blood being rarely found. The 

 hsemorrhagic-like spots on the liver are almost pathogno- 

 monic of death from tuberculin. 



Absolute alcohol precipitates the active principle of 

 tuberculin in the form of a whitish flocculent precipitate 

 which chemically consists of proteoses. This precipitate, 

 re-dissolved, is made use of in the ophthalmic reaction 

 (p. 330). Tuberculin applied to the scarified skin also 

 gives a cutaneous reaction in tuberculosis (p. 330). 



Tuberculin R, or TR, new tuberculin, is prepared from 

 young and virulent cultures of the tubercle bacillus. The 

 growth is collected, dried in vacuo, and triturated by 

 machinery. Of the triturated material, 1 grm. is treated 



