MODE OF SPREAD OF THE DISEASE 449 



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 insusceptible to inocula- 

 tion by the ordinary method. Durham, by using the intra- 

 cerebral method of inoculation, has, however, succeeded in 

 raising the virulence so that the organism is capable of produc- 

 ing in guinea-pigs on intra-peritoneal injection illness with some- 

 times a fatal result many weeks afterwards. An interesting 

 point brought out by these experiments is that, in the case of 

 animals which survive, the micrococcus may be cultivated from 

 the urine several months after inoculation. 



Mode of Spread of the Disease. The work of the recent 

 Commission has 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, the organism 

 was found when the animals appeared healthy and there was 

 no physical or chemical change 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 mon- 

 keys 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 

 rendered practically certain that the human subject was infected 

 by means of such milk, and the result of preventive measures 

 by which milk was excluded as an article of dietary amongst 

 the troops in Malta has fully borne out this view. After such 

 measures were instituted, the number of cases in the second 

 half of 1906 fell to 11 per thousand, as contrasted with 47 

 per thousand in the corresponding part of the preceding year. 

 The various facts with regard to the epidemiology of the disease 

 have thus been cleared up. For example, it is more prevalent 

 in the summer months, when more milk is consumed, and there 

 is a larger proportion of cases amongst those in goad social 

 29 



