240 VETERINARY HYGIENE 



years, 78 were affected with tuberculosis, 13 of these cases were due 

 to bovine tubercle bacilli, and in 9 of them death was due to this 

 cause. S. Griffith noted that in 7 out of 35 cases affecting children 

 under twelve years of age bovine tubercle bacilli were present, and 

 all of these were found in children under four years of age. 

 Mitchell* in Edinburgh found that of 72 cases occurring in children 

 under twelve years of age, 65 were due to bovine tubercle bacilli, 

 and 36 of these occurred in children under five years of age. 

 Finally, Eastwood and Griffith have examined a series of 155 

 patients under ten years of age suffering from bone and joint tuber- 

 culosis and isolated bacilli of the bovine type from 45, or 29 per cent. 

 Further, of 17 cases of tuberculosis affecting the urino-genital 

 system described by the same observers, bovine tubercle bacilli were 

 isolated from three. 



IMMUNITY. Though actual recovery from tuberculosis is prob- 

 ably rare, a considerable degree of resistance is developed in animals 

 during the course of an attack. Many different methods have been 

 practised in the past with the object of producing immunity in 

 healthy animals. The first and most important of these was that 

 introduced by von Behring, which consisted of giving animals two 

 intravenous injections of living human tubercle bacilli with an 

 interval of three months between the two operations. The method 

 was practised on a very large scale and a considerable degree of 

 immunity was established in vaccinated animals, but unfortunately 

 it was found that injected bacilli might remain latent in the animal's 

 body for long periods. In the case of milch cows, they have been 

 found to be excreted with the milk even though the vaccination was 

 carried out soon after birth. This renders the method unsafe, and 

 in the words of M'Fadyean " it may be questioned whether at least 

 in the case of females the operation should not now be prohibited 

 by law. Further, vaccination is a hindrance rather than a help 

 when the object aimed at is the building up a tubercle-free herd. 

 It is a hindrance because its employment is apt to draw attention 

 away from the supreme importance of isolation as a safeguard 

 against infection of healthy animals, and because it seriously inter- 

 feres with the subsequent use of tuberculin in order to determine 

 whether the vaccinated animals have remained free from infection 

 with bovine bacilli or not." In experiments with calves, avian 

 tubercle bacilli injected intravenously have also been shown to be 

 capable of conferring a certain degree of immunity against sub- 

 sequent test inoculations with bovine tubercle bacilli, but the method 

 has not been put into practice on a very large scale and the pro- 

 *Journ. Comp. Path., 1914, Vol. XXVII., p. 85, Abs. 



