Pathogenesis 357 



pumice stone are washed and then dried in the sun, and then 

 allowed to absorb a mixture of one ounce of meat-extract and 

 two ounces of water. This pumice stone is then placed in 

 wide-mouthed bottles and placed in the autoclave. Each 

 bottle is provided with a stopper through which pass two 

 tubes, the one tube opening into the autoclave and reaching 

 nearly to the bottom of the bottle, and the other leading from 

 the top of the bottle into a condenser adjoining. When the 

 cover of the autoclave is adjusted and the steam admitted, 

 then in the case of each bottle, the steam passes by the one 

 tube to the bottom of the bottle, and rising through the 

 pieces of pumice stone, the steam, carrying with it the volatile 

 constituents of the meat-extract, reaches the condenser by 

 the second tube. The vapor in the condenser yields the 

 salt-free nutrient medium in the proportion of two litres to 

 each ounce of meat-extract originally used. The medium is 

 collected from the condenser in sterilized Pasteur flasks which 

 are kept plunged during the process in a freezing mixture 

 in order to condense some of the volatile alkaloids from the 

 beef that would otherwise escape. The nutrient fluid is 

 now inoculated with the bacillus of leprosy arid the flasks 

 kept at 37 for from four to six weeks; at the end of this 

 period when examined the flasks should present a turbid 

 appearance with a stringy white deposit." 



Pathogenesis. Nearly all attempts to infect the lower 

 animals with leprous materials either purulent matter or 

 scraps of solid tissue from lepers, or with cultures of the 

 several bacilli that have been isolated have failed. 



Melcher and Artmann introduced fragments of lepra 

 nodules into the anterior chambers of the eyes of rabbits, 

 and observed the death of the animals after some months, 

 with what they considered to be typical leprous lesions of 

 all the viscera, especially the cecum; but the recent careful 

 experiments of Tashiro * show that the lower animals are 

 entirely insusceptible to infection with the lepra bacillus, 

 and that when they are inoculated the bacilli persistently 

 diminish in numbers and finally disappear. 



Very few instances are recorded in which actual inocula- 

 tion has produced leprosy in man. Arning was able to 

 experiment upon a condemned criminal, of a family entirely 

 free from the disease, in the Sandwich Islands. Fragments 



*' Centralbl. f. Bakt. u. Parasitenk." (Originale), xxxi, No. 7, p. 

 276, March 12, 1902. 



