RELATIONS TO THE DISEASE 503 



though the organism multiplies to a certain extent. Outside 

 the body the organism has considerable powers of vitality, as it 

 has been found to survive in a dry condition in dust and clothing 

 for a period of two months. 



Relations to the Disease. — There is in the first place ample 

 evidence, from examination of the spleen, both post mortem and 

 during life, that this organism is always present in the disease. 

 The experiments of Bruce and Hughes first showed that by 

 inoculation with even comparatively small doses of pure cultures 

 the disease could be produced in monkeys, sometimes with a 

 fatal result. And it has now been fully established that inocula- 

 tion with the minutest amount of culture, even by scarification, 

 leads to infection both in monkeys and in the human subject. 



Rabbits, guinea-pigs, and mice are, as a rule, insusceptible to 

 inoculation by the ordinary method, though some strains may 

 produce pathogenic effects. Durham, by using the intracerebral 

 method of inoculation, however, succeeded in raising the viru- 

 lence, so that the organism is capable of producing in guinea- 

 pigs on intraperitoneal injection illness with sometimes a fatal 

 result many weeks afterwards. Eyre also, by increasing the* 

 virulence by intracerebral inoculation, was able to produce 

 infection in various animals, especially on intravenous injection. 



Mode of Spread of the Disease. — The work of the 1904 

 Commission resulted in establishing facts of the highest 

 importance with regard to the spread of the disease. In the 

 course of investigations Zammitt found that the blood of many 

 of the goats agglutinated the micrococcus melitensis, and 

 Horrocks obtained cultures of the organism from the milk. 

 Further observations showed that agglutination was given in 

 the case of 50 per cent, of the goats in Malta, whilst the organism 

 was present in the milk in 10 per cent. Sometimes the organism 

 was present in enormous numbers, and in these cases the animal 

 usually appeared poorly nourished, whilst the milk had a some- 

 what serous character. In other cases, however, it was found 

 when the animals appeared healthy, and there was no physical 

 or chemical change discoverable in the milk. It was also 

 determined that the organism might be excreted for a period 

 of two to three months before any notable change occurred in 

 the milk. Agglutination is usually given by the milk of infected 

 animals, and this property was always present when the micro- 

 coccus was found in the milk. It was, moreover, found that 

 monkeys and goats could be readily infected by feeding them 

 with milk containing the micrococcus, the disease being contracted 

 by fully 80 per cent, of the monkeys used. It was therefore 



