y98 Trypaniisoiue. Diseases. 



varieties, aiul of several diseases. Considering the marked 

 resemblance of the morphological characteristics of most of the 

 parasites belonging to this group, there exists a possibility that 

 the diseases discnssed in the first part (Nagana, Surra) repre- 

 sent a pathological unit, while the unimportant differences noted 

 in the others depend chiefly on the variability in virulence of 

 the several kinds of trypa'nosomes, likewise also on the geo- 

 graphical and climatic conditions, whereby the differences in 

 the mode of natural infection, as well as the course of the disease 

 can be explained readily. In deference to the general concep- 

 tion, the diseases considered at present as independent affec- 

 tions will be treated separately, after previously" explaining 

 these points of view. 



Besides the pathogenic trypauosoines there exists a great number 

 of others which occur as harmless 1)lood parasites in domestic animals 

 and in other species of animals. 



General Morphology and Biology of the Causative Agents. 



The trypanosomes are unicellular, animal microorganisms, 

 containing a nucleus, a blepharoplast, and a flagellum. They 

 propagate by longitudinal division, possibly also sexually. The 

 parasites known to be producers of disease possess slender, 

 spindle-shaped bodies, the posterior ends of which are more 

 or less blunt; they are enclosed by a periplastic membrane. 

 The parasites are mostly 21-35 /^ long, and li/o-S /^ broad, in 

 the middle portion they contain a spherical or oval nucleus and 

 close to the posterior end a shining nucleolus (centrosoma, 

 blepharoplast, flagella root, trophonucleus) (see Table IX). 

 From the latter a fine flagellum runs out, which extends forward 

 on the outside borders along the undulating membrane, wdiich 

 is present on one side of the body, and terminates in a free 

 portion at the antet^ior point of the Ijody. In the fine granulated 

 protoplasm there are distributed one or more vacuoles, and 

 also various sized granules in varying numbers. 



By means of lashing movements of the flagellum and spiral 

 contraction, the trypanosomes are capable of lively motions 

 in fluid as Avell as in the blood between the blood corpuscles, 

 usually in the direction of the flagellated extremities. 



On the addition of certain substances, especially of immune serum, 

 the trypanosomes unite in pretty rosette shapes (agglomeration), by 

 approaching each other, usually with the posterior ends, in radiating 

 arrangement and executing whip-stroke movements with the free flagel- 

 lated extremities directed outwardly. 



Propagation occurs thus that first the centrosome, then 

 the flagellum and nucleus split longitudinally in two parts, and 

 finally the plasma body breaks into two halves from front to 

 back. Sometimes the division of the ])ody does not follow that 

 of the centrosome and the flagellum immediately, so that irregular 



