20 PROTOZOA AND DISEASE 



Spirochczta Ziemanni. The Sp. Ziemanni, which was discovered 

 by Danilewsky 1 in 1891 in the blood of Athene noctua, and later 

 described and figured by Ziemann, 2 preys on both the white 

 corpuscles and the erythroblasts of its warm-blooded host, becoming 

 attached to them by its hinder end, and surrounding them by a thin 

 mantle 3 of its own ectoplasm; erythroblasts 4 thus surrounded are 

 prevented from undergoing their proper development into red 

 corpuscles. When the parasite reaches maturity it casts off its outer 

 envelope, and also the remains of the blood-corpuscle, and, like 

 the Trypanosoma noctua, then either undergoes subdivision, swimming 

 freely in the blood as a flagellated organism, or, when taken up into 

 the alimentary tract of the gnat, undergoes further development. 

 The changes of the different modifications of Sp. Ziemanni in the 

 gnat have been traced by Schaudinn. The female and male forms 

 undergo development similar to that observed in Plasmodium, Pro- 

 teosoma, and T. noctuce that is, the females undergo fertilization by 

 union each with a microgamete. The ookinets thus formed can be 

 distinguished by their nuclear structure and other features into three 

 kinds asexual, male and female. The course of events in the first 

 of these is represented in Fig. 4. The nuclear changes that accom- 

 pany these processes are very complex. The resulting small 

 trypanosomes become highly elongated and their flattened bodies 

 spirally twisted, thus assuming a typical spirochaeta form. The 

 spirochaetae increase in numbers by longitudinal division, and they 

 have alternating periods of activity and rest. These features are 

 shown in Fig. 5. Schaudinn observed that subdivision proceeded 

 much more rapidly than growth, so that in the end countless very 

 minute organisms, only just visible by the highest powers of the 

 microscope, were present, and he surmised that the same process 

 may lead to invisible organisms that would pass the finest filters, 

 and in this way a particulate virus that is filterable is more than 



1 Danilewsky, abstract in Cent, fur Bakt., 1891, p. 120. 



2 Ziemann, ' Ueb. Malaria und andere Blutparasiten,' Jena, 1898. 



3 This mantle contains eight longitudinal bands or ' myonemes.' 



4 The preference shown by Sp. Ziemanni for the erythroblasts, or immature 

 red blood-corpuscles, explains their abundance in the bone-marrow and the spleen. 



