CHAPTER XVI. 



SPIROCHETES. 



The diseases produced by spirochetes are now referred 

 to as spirilloses or spirochetoses, and fall into (following 

 Muir and Ritchie) two main groups : (i) The human 

 spirillar fevers, and the corresponding affections of various 

 animals ; (2) Syphilis and yaws, and the ulcerative and 

 gangrenous conditions apparently caused by spirochetes 

 (e.g., Vincent's angina). In the first group, blood infec- 

 tion is the rule, and the organisms are, in most cases if 

 not in all, transmitted by blood-sucking ecto-parasites. 

 In the second group, the organisms are primarily tissue 

 parasites, and later show blood infection, and are mainly 

 spread by direct contact. As regards general morphology, 

 staining reactions, and conditions of growth and culture, 

 the various spirochetes present common characters, and 

 their classification with bacteria or protozoa is still a 

 matter of doubt. 



Spirillum Obermeieri or Sp. of relapsing fever (Ober- 

 meyer, 1873) Is now usually regarded as a spirochete, and 

 known as the Spirochaeta recurrentis. It is found in the 

 blood of patients suffering from " relapsing fever " from 

 shortly before the onset of the pyrexia until shortly before 

 the crisis, and similarly in the relapses. The relationship 

 of the organism to the disease has been proved by the 

 injection of spirochetes into the blood-stream causing 

 the typical attack, both in the human subject and in 

 monkeys ; also in white mice and rats, but in these and 

 in monkeys, relapse is rare. Sp. Obermeieri is a delicate 

 spiral thread, 7 to 9 micra long by about 1 micron thick, 

 but the size varies from one-half to nine times the diameter 

 of a red blood corpuscle (7 micra). The windings like- 

 wise vary from 4 to 10 or more. It stains with watery 

 basic aniline dyes, somewhat faintly, but best with the 

 Romanowsky stains. It shows a homogeneous cell body 



