CULTIVATION 527 



spirals, but these are somewhat irregular aud often poorly 

 marked (Fig. 161); not infrequently the ends form small 

 hooks. It is motile, the movements being rotatory, undulatory, 

 and also to and fro. It can be studied by all the microscopic 

 methods already described in the case of the sp. pallida (p. 524). 

 Cultivation. — The organism was first successfully cultivated 

 in Noguchi's medium for sp. pallida, in which the initial growth 

 survives for three to six weeks. The medium remains clear and 

 does not yield any odour. Later it was grown on solid media, 

 blood agar and blood gelatine, the latter being the more suitable. 

 The limits of growth are wide, namely, 15-37° C, the optimum 

 temperature being 22-25° C. Noguchi recommends the follow- 

 ing media as suitable ; he finds that the addition of sterile tissue 

 does not improve the growth : — 



(a) Rabbit serum, two parts ; Ringer's solution or 0'9 per cent, sodium 

 chloride solution, six parts ; citrated rabbit plasma, one part.' 



(b) The same with the addition of one to two parts of neutral or slightly 

 alkaline agar (2 per cent. ), which should be liquefied and added when 

 quite hot (60-65° C.) in order to get a uniform mixture of the agar. 



Both media are covered with a layer of sterile liquid paraffin, and inocu- 

 lation is made through the paraffin. In these media growth produces 

 slight turbidity. 



Relations to the Disease. — The organism occurs both in the 

 blood and in the organs. In the former it is found in the first 

 four or five days of the disease ; thereafter it gradually disap- 

 pears, and in the second week, when jaundice is most marked, it 

 cannot be detected. The best method of demonstrating its 

 presence is to draw off some blood, say, 3 c.c, and inject it into 

 the peritoneal cavity of the guinea-pig, in which animal it pro- 

 duces an infection and can easily be found (vide infra). It is 

 rarely present in the blood in the human subject in numbers 

 sufficient to allow its detection by microscopic examination. 



Of the internal organs the liver contains the organisms in 

 largest quantities ; they may be also found in the suprarenals, 

 and, especially at a later stage, in the kidneys. In all the 

 organs in the human subject the spirochaetes are scanty, they 

 are often somewhat irregular and degenerated in appearance, 

 and often in the interior of the special cells. These facts have 

 been explained as being the result of the formation of anti- 

 substances, which drive them from the blood and interstitial 

 tissues. Their late occurrence and persistence for some time in 

 the kidneys are comparable with what occurs in the natural 

 infection of the rat without the occurrence of disease symptoms 

 (vide infra). The spirochete is also excreted in the urine. 



