916 THE SPIROCHETES 



the medium was seeded with a fragment of syphilitic rabbit's testicle, and the whole was 

 covered with a layer of liquid paraffin. Incubation was carried out anaerobically at 37° C. 

 The primary mixed culture was later purified by growth in serum agar stabs containing 

 fresh rabbit tissue ; in this medium a hazy zone around and above the tissue became 

 perceptible in about 3 days due to proliferation of the spirochsetes ; by subculture from this 

 zone he eventually succeeded in obtaining pure cultures of the organism. The following 

 year Noguchi (19126) succeeded in cultivating Trep. pallidum directly from human lesions. 

 The medium he used consisted of a mixture of 2 parts of nutrient agar and 1 part of ascitic 

 or hydrocele fluid, put up in tubes 20 X 2 cm. in size, each containing at the bottom a 

 piece of sterile rabbit kidney or testicle. Material from a chancre, condyloma, or skin 

 papule was inoculated into the tube, and was covered with liquid paraffin. The organisms 

 produced a slight haze round the kidney and could be picked off for purification. In fluid 

 medium growth occurred very slowly and continued for several ^^eeks. The pure cultures 

 were inoculated into monkeys, and proved to be pathogenic. According to Gates (1923), 

 surface colonies may be obtained on 6 per cent, rabbit blood agar plates incubated anaerobic- 

 ally. Colonies are said to be well developed in about a week at 37° C, and to be surrounded 

 by a zone of complete hsemolysis. Other media have since been used with apparent 

 success (Gates 1923, Weiss and Wilkes- Weiss 1924, Hoder 1930, Aksjanzew-Malkin 1933). 

 It must be pointed out, however, that several reputable workers have entirely failed to 

 cultivate Trep. pallidum. Among them is Jahnel (1934), who maintains that the so-called 

 cultures of this organism are in fact cultures of a saprophytic spirochsete (see also Gohring 

 1940). According to Kast and Kolmer (1940), no one has yet succeeded in devising an 

 in vitro method of cultivation in which the virulence of the organisms for the rabbit is 

 preserved. The difficulty in practice of obtaining in vitro cultures is so great that for 

 preserving the organism it is usual to employ in vivo methods. Brown and Pearce (19216) 

 found that if rabbits are infected with syphiHs, the organisms are carried to the lymphatic 

 glands and remain there indefinitely. When the strain is required for use, a popliteal 

 gland is excised, ground up in a mortar with saline, and injected intratesticularly into 

 fresh rabbits. Kolleand Schlossberger (1928) have moreover shown that Trep. pallidum 

 remains alive in the tissues of mice for an indefinite period, and can be recovered at any 

 time from the glands, spleen, or brain. Using this method they made three passages 

 through mice in 19 months, and found that the organisms remained fully virulent for 

 rabbits. 



Resistance. — Very susceptible to heat. According to Boak, Carpenter, and Warren 

 (1932), saline suspensions of infected rabbit testicle are sterilized by exposure to 39° C. 

 for 5 hours, 40° C. for 3 hours, 41° C. for 2 hours, and 41-5° C. for 1 hour. Dies out rapidly 

 in stored blood, unless frozen, so that the chances of transmitting syphilis with stored 

 blood, plasma, or serum are very small (see Selbie 1943). 



Antigenic Structure. — -Little known. Noguchi and Akatsu (1917), using agglutination 

 and complement fixation, obtained evidence of an affinity of Trep. pallidum to Trep. 

 calligyrum. They also observed a certain amount of heterogeneity between different 

 strains of pallidum. There is said to be a strain-specificity in cultures of pallidum (see 

 Georgi el al. 1929), but in view of the serious criticisms that have been made on the sup- 

 posed cultivation of this organism, it would be dangerous to lay too much stress on this 

 statement. 



Pathogenicity of Treponema pallidum for Animals. 



Rabbits. — Haensell in 1881 was the first to produce keratitis in rabbits by inoculation 

 of syphilitic material into the anterior chamber of the eye. His observations were neglected 

 for over 20 years, when they were confirmed by Bertarelli in 1906 ; the syphilitic nature 

 of the lesions was proved by the demonstration in them of Treponema pallidum. The 

 receptivity of the rabbit's eye has been confirmed by numerous workers. Bertarelli ( 1907, 

 1908) moreover showed that it was possible to carry over syphilis from one animal to 

 another. According to Uhlenhuth and Mulzer (1913) inoculation of a small piece of 



