MICROBIAL DISEASES OF MAN AND ANIMALS. 623 



The bacteria of leprosy were first described by Hansen in 1879 and 

 almost at the same time Neisser published similar descriptions. Culti- 

 vation of Bad. leprcc has been successful in the hands of Clegg, Duval 

 and others. 



The microorganisms can be shown in tissue by the use of the Ziehl- 

 Neelsen or Gabbet methods. 



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

 usually appears somewhat longer ($/j. to 7/1) and thicker (about 0.5/1) 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 Bad. lepr<z stains more readily and also decolor- 

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

 decolorize them while Bad. tuberculosis resists. The 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 pheno- 

 Iphthalein. 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 ele- 

 vated centrally, with an irregular wavy margin and attaining a diameter of 2 mm. 

 Older cultures on glycerin agar are moist and abundant, 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 ordi- 

 nary vegetative bacteria, so that cultures may be freed from contamination by the 

 latter by simply heating to 60 for one 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 symptom of illness and must be killed in order to find the lesion. 

 More recently Duval has produced an apparently typical leprosy in 

 monkeys by repeated injections of artificial cultures. 



It is generally considered that 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. Comple- 

 ment deviation with various antigens has been investigated and indicates 



