SYPHILIS 233 



made by different observers, in some cases with reported 

 successful result, it is to the papers of Metchnikoff and Roux 

 (1903-5) that we owe most of our knowledge. These observers 

 have carried on a large series of observations, and have shown 

 that the disease can be transmitted to various species of monkeys. 

 Of these the anthropoid apes are most susceptible, the chimpanzee 

 being the most suitable for experimental purposes. Their 

 results have been confirmed by Lassar, Neisser, Kraus, and 

 others. Inoculations made by scarification resulted in the 

 production of typical primary lesions in all of more than twenty 

 animals used. The primary lesion is in the form of an indurated 

 papule or of papules, in every respect resembling the human 

 lesion. Along with this there is a marked enlargement and 

 induration of the corresponding lymphatic glands. The primary 

 lesion appeared on an average about thirty days after inocula- 

 tion, and secondary symptoms appeared in rather more than 

 half of the cases after a further period of rather longer duration. 

 These were of the nature of squamous papules on the skin, 

 mucous patches in the mouth, and sometimes palmar psoriasis. 

 As a rule, the secondary manifestations were of a somewhat 

 mild degree, and in no instance up to the present has any 

 tertiary lesion been observed. By inoculation from the secondary 

 lesions, the primary manifestations with their typical characters 

 have been reproduced. The orang-outang has been found to be 

 less . susceptible, whilst Roux's experiments on the gorilla have 

 been too few to admit of any conclusion. The disease may also 

 be produced in baboons and macaques (macacus sinicus is one of 

 the most susceptible), but these animals are less susceptible. 

 In the case of many of them no result follows, and when a lesion 

 is produced it is only of the nature of a primary papule, 

 secondary manifestations never appearing. There is thus no 

 doubt that the disease may be produced in apes, and, to speak 

 generally, the severity of the affection increases according to the 

 nearness of the relationship of the animal to the human 

 subject. 



The production of the disease, experimentally, has supplied 

 us with some further facts regarding the nature of the virus. 

 It has been shown repeatedly that the passage of fluid con- 

 taining the virus through a Berkefeld filter deprives it completely 

 of its infectivity. In other words, the virus does not belong to 

 the ultra-microscopic group of organisms. The virus is also 

 readily destroyed by heat, a temperature of 51 C. being 

 fatal. With regard to the production of immunity, very little 

 of a satisfactory nature has so far been established. It has been 



