MASTIGOPHORA 



193 



inch to gib mcn m length and are about J-^ O -Q inch 

 wide. They move by a sinuous, jerking, boring action. 

 Division takes place by longitudinal splitting, probably 

 beginning at the hind end and proceeding along the undu- 

 lating membrane. The true nucleus shows its division late. 

 The human trypanosoma has resisted artificial cultivation 

 until very recently, and at the present time it is very difficult 

 to cause development in the laboratory. Other forms of 

 these protozoa have been grown with comparative ease. 

 Most animals may be the hosts of trypanosoma; in some there 

 will be disease, in others the organisms live as harmless 



FIG. 62. Trichomonas vaginalis. 

 (BlochmaDn.) 



FIG. 63. Lamblia intestinalis. 

 (Schewiakoff.) 



commensals. The modern treatment consists in using an 

 arsenic -preparation called atoxyl. Numerous attempts have 

 been made to produce a serum by injecting animals with 

 trypanosoma. Sera thus obtained have a slight beneficial 

 effect upon the lower animals, but have not proved of great 

 value with human beings. The injection of attenuated 

 cultures has raised the resistance of certain lower animals. 

 The fact that some resistance can be attained by attempts 

 toward the production of active and passive immunity indi- 

 cates that trypanosoma exert their action by some poison. 

 Whether it be in their bodies or elaborated in the juices 

 about them is not known. 

 13 



