Pathogenesis 535 



The culture fluid remains perfectly clear although the spiro- 

 chaetae distribute themselves throughout the medium. The sUghtest 

 cloudiness indicates contamination. No odor is given off, and 

 the ascitic fluid is not coagulated. The multiplication of the spiro- 

 chaetae does not begin at once, but only after several days and some- 

 times not for a week or two. The cultivated organism does not 

 differ from that obtained directly from the animal body except that 

 when multiplication is at its height the organism is very short 

 and has brisk movements. Sometimes two are connected and some- 

 times from 8 to 15 may be collected about some granular substance 

 forming a kind of rosette, but maintaining very brisk movements. 



Noguchi* thinks that the most reliable procedure for securing 

 initial growth is to produce strands of loose fibrin in the fluid culture 

 media by using a small quantity of citrate plasma in combination 

 with the diluted or undiluted serum of a suitable animal. Th^ dilu- 

 tion of the serum made in any proportion above i : 10 by adding 

 sterile (0.9 per cent.) saline Ringer solution or even plain water. 

 For obtaining the spirochsetal material for inoculation, the citrated 

 blood derived from the heart of a guinea-pig having the disease is 

 best although an emulsion of kidney or liver may also be used. He 

 obtained a good growth from infected guinea-pigs' blood in dilution 

 as high as i : 100,000. 



Noguchi believes that blood cultures for diagnostic purposes in 

 human cases are feasible and for the purpose recommends two media. 

 The first is rabbit serum i part 4- Ringer's solution or 0.9 per cent, 

 sodium chloride solution 3 parts -|- citrated rabbits' plasma 0.5 

 part, covered with a thin layer of sterile parafline oil. The second 

 is the same except that 0.5-1 o parts of neutral or slightly alkaline 

 2 per cent, agar-agar are added while liquid and at about 6s°C. 

 and mixed well. These media, because of the parafSne oil layer, can 

 be preserved at room temperature for many months in a cool place. 



In the case of an infected guinea-pig, the detecting of the spiro- 

 chseta in the blood can be made in forty-eight to seventy-two hours 

 if the culture tubes are kept at 3o°-37°C. The search for the organ- 

 isms should be made within the aerobic zone immediately below the 

 surface (1.0-1.5 cm.), because, according to Nbguchi's experience the 

 organism is an ohligatory aerobe unable to grow in the absence of 

 oxygen. The growth is visible as a distinct haze. 



Pathogenesis. — The spirochasta is pathogenic for man, guinea- 

 pigs, rats and mice. The guinea-pig seems to be the most susceptible 

 animal — even more so than man. Rabbits are almost insuscept ble. 



Distribution in the Animal Body .—This has been made the subject 

 of a careful investigation by Kaneko and Akuda,t who follow Inada 

 and Ido in dividing the disease into three stages (i) the febrile, (2) 

 the icteric, (3) the convalescent. In the febrile or first stage, lasting 



* Jour. Exp. Med., 1917, xxv, 758. 



t Jour. Exp. Med., 1917, xxvi, No. 3, p. 325. 



