TREPONEMA PALLIDUM 241 



from 3 to 12 turns or bends, and its ends are delicately pointed. 

 Its curves form a large arc of a small circle; the Sp. refringens 

 curves form a small arc, frequently irregular, of a larger circle. 

 It multiplies by both transverse and longitudinal division. As 

 this organism is stained with difficulty it requires a special one, 

 that of Giemsa yielding the best results. Aniline gentian violet, 

 Romanowsky's, and Leishman's stains also color it. It may be 

 stained in tissues by silver and pyrogallic acid methods. 



Habitat. It has not been found in tissues of normal persons, or 

 those ill with carcinoma, tuberculosis, etc., but only in the tissues 

 of individuals suffering with syphilis. It is a strict parasite. 



Vitality. The organism is readily destroyed by the ordinary 

 disinfectants and dies, after a few minutes' exposure to 5oC. 



The Treponema pallidum has now fulfilled the postulates of 

 Koch. It can be cultivated from human lesions (with some 

 difficulty to be sure), it can be implanted in animals (monkeys 

 and rabbits) and there reproduce syphilitic lesions; and it can be 

 re-cultivated from them. In these experimental diseases it re- 

 tains the proper morphology. According to Noguchi there are 

 two types, a slender and a stout, which breed true to these charac- 

 ters and correspond to slight pathogenic variations. Noguchi 

 succeeded in cultivating the Tr. pall, in pure culture by using 

 the juice from human or monkey's lesions or from the syphilitic 

 orchitis of rabbits. This he grows in serum water or serum agar 

 to which has been added fresh tissue of rabbit. The organism 

 grows as fine fibrils in arborescent colonies. These can be selected 

 pure by cutting the tube and the agar column. Motion is of 

 screw and serpentine character. No odor or spores are produced. 

 This organism must be imagined and remembered as a corkscrew 

 and not a waving line. The Gram stain is negative. 



From the cultures of this organism a toxic extract can be ob- 

 tained which, when rubbed into the skin of a syphilitic in the 

 late stages, gives a typical skin reaction, luetin and the luetin 

 reaction. 



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