198 



KNOWLEDGE. 



May, 1913. 



bord 



ering 



the 



body of the organism, namely, the Micronucleus. 



This occurs usually quite posteriorly in the 

 body, and it is thought that its function is to 

 govern the movements and reproduction phases, and 

 hence it is sometimes called the " kinetonucleus." 



The "undu- 

 lating-mem- 

 brane " is a fin- 

 like ridge or fold 

 of the bod\' pro- 

 toplasm, and lies 

 to one side of 

 the body. Being 

 longer than the 

 body-length, as 

 will be seen in 

 the illustrations, 

 it is cast into 

 many wave-like 

 folds. It is a 

 very delicate 

 membrane of 

 very variable 

 width, being in 

 some trypano- 

 somes so narrow 

 that it is almost 

 impossible to 

 make out : at 

 other times it is 

 considerably 

 broader even 

 than the body- 

 width. It con- 

 stitutes an organ 

 for swimming. 



From the mi- 

 cronucleus there 

 arises a thread 

 of nuclear ma- 

 terial called the 

 " fl age 1 1 u m," 

 which runs for- 

 ward anteriorly 

 along the bodv, 



Lony $ Slender. 



extreme edge of 

 the undulating- 

 membrane, as 

 far as that goes, 

 and then pro- 

 ceeding beyond 

 the anterior end 

 as a free thread 

 or lash, called 

 the "free flagel- 

 lum." This may 

 extend to twice the body-length. Its purpose is also 

 for swimming. 



Trypanosomes are essentially very " lively " 

 creatures, and most, while capable of swimming 

 actively in the blood by means of the undulating- 



Short £ Stumpy. 



By permission of The Tropical Disease. 



Figure 204. 

 Trypanosoma gambiense X 2,000, showing types. 



membrane, and free flagellum, are also capable of 

 wriggling and twisting movements. All the move- 

 ments in health)- trypanosomes are generally very 

 violent, and the blood corpuscles are thrown in all 

 directions as the organisms dart here and there. 



The movement 

 of the undulat- 

 ing membrane 

 has been very 

 aptly compared 

 to tile flapping 

 of a boat's sail 

 that has " lost 

 the wind." It is 

 an exceedingly 

 graceful move- 

 ment, and 

 travels as a rip- 

 pling wave over 

 the entire mem- 

 brane. The 

 direction of the 

 waves vary ac- 

 cording as to 

 whether the 

 animal travels 

 backwards or 

 forwards. The 

 movements of 

 the flagellum 

 are almost im- 

 possible to make 

 out as only their 

 effects on the 

 surrounding 

 medium give 

 one any indi- 

 cation of what 

 they are ; but 

 the\- must 

 obviously be 

 some systema- 

 tic series if 

 they are to 

 benefit progres- 

 sion. It is due 

 to the rapidity 

 of the move- 

 ments of try- 

 panosomes, that 

 trypanosomes, 

 while they are 

 living, are such 

 extremely diffi- 

 cult subjects to 

 study. In the 

 case of T. vivax, 

 a particularly lively creature, all that can be seen in 

 the medium in which it exists are rocket-like 

 paths as the trypanosome dashes across the field of 

 the microscope. 



Trypanosomes multiply in the blood of their hosts 



After a plate by Lady 

 Bruce (Royal Society Proc. B. vol. 84.) 



