MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 775 



In tissue the bacterium closely resembles the bacterium of tuberculosis, but 

 usually appears somewhat longer (sa* to 7/t) and thicker (about 0.5^) straighter and 

 less beaded. Flagella have not been demonstrated. The bacterium can be stained 

 with the ordinary aniline dyes. It is Gram-positive. The staining reactions on the 

 whole are like those of Bad. tuberculosis but Baci. lepra stains more readily and also 

 decolorizes more readily; 30 per cent nitric acid followed by 95 per cent alcohol will 

 totally decolorize them while Bact. tuberculosis resists. Ihe optimum temperature 

 for growth ranges from 32° to 35° when grown in symbiosis with amoebae. The 

 reaction of the media upon which successful isolation takes place is i to 1.5 per cent 

 alkaline to phenolphthalein. In recently isolated cultures growth is extremely 

 slow and appears on the surface of the special media in four to six weeks as moist 

 grayish-white colonies elevated centrally, with an irregular wavy margin and 

 attaining a diameter of 2 mm. Older cultures on glycerin agar are moist and abund- 

 ant, and develop an orange-yellow" pigment. In glycerin broth a thin membrane 

 is formed at the surface after several weeks, while a small amount of sediment 

 collects at the bottom of the tube leaving the medium clear. The resistance to 

 heat is much greater than that of ordinary vegetative bacteria, so that cultures 

 may be freed from contamination by the latter by simply heating to 60° for 6ne 

 hour. The resistance to drying is probably considerable. 



Human leprosy appears to be confined naturally to man and only 

 lately has the disease been transmitted artificially to animals. In the 

 Japanese dancing mouse, and less frequently in the white mouse and the 

 monkey small nodules may be found on the peritoneum about four to 

 eight weeks after intraperitoneal inoculation. The animals do not show 

 any sjmiptoms of illness and must be killed in larder to find the lesion. 

 More recently Duval has produced an apparently typical leprosy in 

 monkeys by repeated injections of cultures from artificial media. 



It is generally considered thfit the usual path of entrance of the bac- 

 terium is the naso-pharyngeal mucous membrane. The organisms seem 

 to be distributed slowly over the body and according. to their location 

 produce the different types of the disease. They are found in the 

 nodules of the nodular type and in the nerve trunks of the anaesthetic 

 type. 



Agglutinins have been demonstrated in the blood of lepers. Com- 

 plement deviation with various antigens has been investigated and 

 indicates an antilipoid immune body which not infrequently gives a 

 positive Wassermann reaction. Lepers react frequently to tubercuHn 

 inoculations and this is not considered to be always due to associated 

 tuberculosis. 



The chief source of elimination of leprosy bacteria is the nasal 



