ANTIGENIC STRUCTURE 911 



the granules, some of which result from a change in the cytoplasm within the 

 organism, and some of which are probably particles of the culture medium adhering 

 to their exterior, are more highly refractile than the rest of the spirochaete, and 

 show up as bright, glistening points. Some observers consider that these granules 

 are not the result of degeneration, but are analogous to bacterial spores, affording 

 a means of continuing life under unfavourable environmental conditions. The 

 evidence in favour of t|;iis view is not convincing. 



The isolation of spirochsetes in pure culture from material in which they are 

 accompanied by bacteria often presents great difficulty. Various methods may 

 be tried, such as rapid subculture, making use of the ability of some species to 

 grow out from the line of inoculation in stab cultures, picking deep colonies, choosing 

 media made selective by the addition of a dye or some other substance, filtration, 

 animal inoculation, and so on (see Seguin and Vinzent 1938, Schiiffner 1940, 

 Wichelhausen and Wichelhausen 1942). 



With some organisms, such as Leptospira icterohceynorrhagice, in vitro culture is 

 remarkably successful ; but with organisms such as Trep. pallidum and Trep. 

 recurrentis it is not so satisfactory. For this reason these organisms are generally 

 preserved by in vivo culture ; that is to say, they are injected into a susceptible 

 animal, which henceforth becomes a chronic carrier, and which can be drawn upon 

 at will for a fresh supply of infective material. A modification of the animal 

 inoculation method, which has proved successful in the cultivation of relapsing 

 fever spirochsetes and Lepto. icterohmmorrliagice, is growth in the developing chick 

 embryo (see Morrow et al. 1938, Chabaud 1939, Oag 1939, Soule 1942). 



Resistance and Metabolism. — The resistance of spirochsetes to inimical agencies 

 is no greater and generally less than that of the vegetative bacteria. Dry heat, 

 moist heat, and desiccation prove quickly fatal, as do comparatively low concen- 

 trations of the chemical disinfectants. It is generally stated that spirochaetes 

 are lysed by a 10 per cent, solution of sodium taurocholate (see v. Prowazek 1907), 

 and all, with the exception of the leptospirse, by a 10 per cent, solution of saponin 

 (Noguchi 1917). Some of the highly parasitic members, such as Trep. pallidum, 

 are unable to survive outside the animal body for more than an hour or two. 

 Indeed this particular organism is extremely susceptible to heat, being destroyed 

 in an hour at 41*5° C. Advantage is now being taken of this property to sterilize 

 the organisms in the tissues by exposure to fever-heat temperatures (see Chapter 81). 

 Spirochaetes in infected tissues may be preserved alive for several months by keep- 

 ing them in the frozen state, preferably at about — 78° C. (Jahnel 1937, Turner 

 1938). 



Practically nothing is known about the metabolism of spirochsetes. Scheff 

 (1935), who made observations on two strains of Trep. pallidum, one of Trep. 

 recurrentis, and one of Trep. anserinum, stated that, when these organisms were 

 grown in a medium containing glucose, they broke down the sugar to lactic acid 

 and CO 2 without using up any of the oxygen. 



Antigenic Structure. — Antigenically, spirochsetes behave very much as bacteria. 

 They give rise on injection to agglutinins, spirochsetocidins, spirochsetolysins, and 

 protective antibodies. Agglutination tests are often conducted by the microscopic 

 method, and observations made on the loss of motility and the clumping of the 

 organisms, which may occur in radiate fashion. Similarly the destruction and 

 lysis of the organisms that frequently follow contact with a highly immune serum 

 are generally watched under the microscope. The macroscopic method, however, 



