IMMUNIZATION BY FEEDING 333 



The bacilli were rapidly washed in distilled water, drained and dried for several 

 days in vacuo over sulphuric acid, then placed in a flat-bottomed flask with pure 

 petroleum ether and glass balls. The flask was placed in a shaking apparatus and 

 the contents shaken for 60 hours. 



The bacilli had then lost their acid-fast properties. The emulsion was dried in a 

 desiccator to remove all traces of the ether from the bodies of the bacilli. 



Tubercle bacilli treated in this manner behave like a very powerful tuber- 

 culin. They kill guinea-pigs in doses of 70 mg. When inoculated several 

 times in doses of from 25-100 mg. into the jugular vein they [are said to] 

 render young calves to a certain degree immune to the bacillus of bovine 

 type. Horses and cattle rendered immune to the inoculation of these bacilli 

 cease to react to the intra-venous inoculation of the various tuberculins. 



(v) Animals vaccinated by inoculating them intra-venously show them- 

 selves very slightly immune to intestinal infection a mode of infection 

 particularly common in nature. Behring, Calmette and Guerin, Roux and 

 Vallee have tried to immunize animals by feeding them with tubercle bacilli 

 and have met with some success. The method is only practicable in the 

 case of young cattle and the resulting immunity is particularly efficient 

 against intestinal infection. Although the immunity is only relative the 

 method gives better results than intra-venous inoculation : the animals 

 remain uninfected for a year when kept with cattle suffering from open 

 lesions. 



Two young calves were fed at intervals of 45 days with 5 and 25 grams of tubercle 

 bacilli of the human type. Four months later failing to react to tuberculin they 

 were fed with 0'05 gram of freshly isolated bacilli of the bovine type : 32 days later 

 they failed to react to tuberculin while two controls reacted in the ordinary way. 



Vallee also immunized a young calf by feeding it, through an cesophageal sound, 

 on two occasions, when it was 2 days and 90 days old respectively, with 20 eg. of a 

 well-made emulsion of a tubercle bacillus of equine origin which was only slightly 

 virulent for guinea-pigs. 



Roux and Vallee, Calmette and Guerin have shown that small doses of virulent 

 bacilli of the bovine type when introduced into the alimentary canal of the calf 

 are absorbed into the mesenteric glands and give rise to a substantial immunity in 

 the animal. A certain amount of risk attaches to this method of immunization 

 (Vallee). 



(vi) For the purpose of producing immunity Arloing uses homogeneous 

 cultures of bacilli of the human type (vide infra) which have lost much of 

 their capacity of producing tubercles ; by submitting them to gradually 

 increasing temperatures Arloing was able to grow them at 43-44 C. These 

 cultures vaccinate calves and appear to act as a true pasteurian vaccine. 



C. Vaccination with a virus of chelonian origin. 



Friedmann showed that a bacillus which he had recovered from a tortoise 

 (p. 297) produced when inoculated beneath the skin of a guinea-pig a typical 

 localized tuberculous focus which soon completely healed while the animal 

 never showed any sign of generalized tuberculosis. Further, guinea-pigs 

 treated in this way resisted the inoculation of a dose of bacilli of the human 

 type which killed control animals in 4-6 weeks. 



In vaccinated guinea-pigs the inoculation of a virus of human origin gave rise 

 to a transitory swelling of the glands and to a caseo- purulent tuberculous focus 

 which healed and left no trace of the injury : when the animals were killed 

 about 3 months later no lesion was found : it is true that small whitish points were 

 seen in the internal organs but these were in no way suggestive of true tubercles 

 and similar lesions are found in animals immune to tuberculosis or vaccinated in 

 various ways against the disease (Koch, von Behring, Neufeld, Thomassen, and 

 others). 



