SYPHILIS 543 



unsettled, though the evidence in favour of the theory is very 

 strong. 



Yet, although the spirochaetes seen developing within the 

 cells of syphilitics very closely resembled the Spirochceta pallida 

 in appearance, and although there was the evidence of the 

 disease in guinea-pigs, and the corollary of the similar intra- 

 cellular parasite developing into spirochaetes in these animals 

 also, proof by inoculation was wanting ; for it is impossible to 

 experiment with syphilis in human beings, and the manifesta- 

 tions of the guinea-pig disease are inconveniently confined to 

 the blood-cells and internal organs. Nevertheless, these inocu- 

 lation experiments soon became possible, and in a very curious 

 way. I was told by Lord Kimberley that the wild rabbits and 

 hares in the county of Norfolk were suffering from a disease 

 named by gamekeepers " rabbit-pox." Very soon afterwards, 

 a paragraph appeared in Country Life (October 6, 191 2) in which 

 it was stated that the wild rabbits on the east coast of Scotland 

 were infected with a peculiar disease. Some of these infected 

 animals were obtained and the disease examined at the Lister 

 Institute. It was soon found by me that these rabbits had a 

 naturally contracted affection similar to human syphilis, though 

 probably not identical with it. And examination showed the 

 presence of similar but smaller intracellular parasites like those 

 which had been already seen in cases of human syphilis, in the 

 guinea-pig disease, and in earthworms. These animals were 

 watched, and the progress of this affection observed. It coin- 

 cided with the progress of syphilis in human beings, except that 

 it is more severe under the natural conditions of rabbit-life, and 

 the animals frequently die when uncared for. Some were treated 

 with salvarsan and mercury, and improvement began at once ; 

 several infected animals have now been apparently cured. 



But, as stated before, it was necessary to prove the deduction 

 that these intracellular parasites are the real causative agents of 

 these diseases. Therefore, a young healthy rabbit was inocu- 

 lated from a diseased rabbit. The inoculation was accomplished 

 by scratching with the point of a contaminated sewing-needle, 

 as a calf-lymph vaccination is performed. In twenty-five days 

 a small sore appeared at the seat of inoculation, and the disease 

 began. In this sore the same intracellular parasites were 

 found, and, finally, free swimming spirochaetes, which appear 

 to be exactly similar to the Spirochccta pallida, were seen by 



