TKANSMISSION OF THE DISEASE TO ANIMALS 521 



even the blood in secondary syphilis. Inoculation is usually 

 made by scarification on the eyebrows or genitals ; the sub- 

 cutaneous and other methods of inoculation, with the exception 

 of intratesticular, give negative results. 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 are marked enlargement and induration of the 

 corresponding lymphatic glands. The primary lesion appears 

 on an average about thirty days after inoculation, and 

 secondary symptoms develop in rather more than half of the 

 cases after a further period of rather longer duration. These 

 are of the nature of squamous papules on the skin, mucous 

 patches in the mouth, and sometimes palmar psoriasis. As a 

 rule, the secondary manifestations are of a somewhat mild 

 degree, and in no instance has any tertiary lesion been observed, 

 though this may be due to the animals not having lived long 

 enough. By re-inoculation from the lesions, the disease may be 

 transferred to other animals. The disease may also be produced 

 in baboons and macaques, but these animals are less susceptible, 

 and secondary manifestations do not appear. The severity of 

 the affection amongst apes would in fact appear to be in pro- 

 portion to the nearness of the relationship of the animal to the 

 human subject. The blood of the infected animals comes to 

 give a positive Wassermann reaction. 



As shown first by Hansell, and afterwards by Bertarelli, the 

 eye of the rabbit is susceptible to inoculation from syphilitic 

 lesions. The material used is introduced in a finely divided 

 state either into the tissue of the cornea or into the anterior 

 chamber, and syphilitic keratitis or iritis, or both, may result, 

 there being a period of' incubation of at least two weeks. 

 Levaditi and Yamanouchi have studied the stages in detail, and 

 find that the spirochsetes remain in the inoculated material un- 

 changed for a time ; then organisation occurs and the spirochsetes 

 multiply, and later still there is a more rapid multiplication and 

 invasion by them of the tissues of the eye. The period of incu- 

 bation is thus not due to the organism passing through some 

 cycle of development, but simply to its requiring certain con- 

 ditions for multiplying; which are not supplied for some time. 

 The testis of this animal is also a convenient site of inoculation, 

 a syphilitic orchitis being set up, and the disease has been 

 maintained by this method through several generations of 

 animals. The intratesticular method has proved of great value 

 in testing the infectivity of suspected material, and by this 

 means it has been shown that spirochsetes from gummata are 



