Tlie Trypanosomes causing Dourine. 



91 



Strains B and C respectively. It is to be observed that this distinction 

 between the strains is much more clearly brought out by an examination of 

 guinea-pigs than of rats. 



Applying the present method of classification, this morphological distinction 

 is at once sufficient to differentiate Strain A from the others. If we adopt 

 Laveran's recent scheme for the classification of pathogenic trypanosomes, 

 Strain A belongs to Group 3 (in which certain individuals have a free flagellum, 

 wbilst others have not), whereas Strains B and C must be classed amongst the 

 trypanosomes forming Group 1 (those in which all the individuals have a free 

 nagellum). 



Moreover, there is a further morphological peculiarity by which Strain A 

 is differentiated from Strains B and C. As is described in our previous 

 paper (loc. tit.), certain of the short forms of the former strain exhibit a 

 posterior nucleus. The phenomenon, so far as we have been able to ascertain, 

 is limited to this strain and does not occur in either of the other two. 



Having satisfied ourselves that Strain A was morphologically distinct from 

 Strains B and C, we examined more minutely the morphology of the two 

 latter strains with a view to ascertaining whether these are different one from 

 the other or whether they are identical. 



Attention has already been called to the fact that in both the strains long 

 free flagellated forms constitute the vast majority of the parasites encountered. 

 There is, however, a point to which we must refer. In the East Prussian 

 strain the cytoplasm is continued in many individuals a considerable distance 

 along the flagellum, so that even the longest forms encountered have 

 frequently a comparatively short portion of flagellum free. Most of the 

 aflagellar or spicule forms in this strain are not " short stumpy " forms 

 properly speaking, but medium or even long forms in which the cytoplasm is 

 carried along the flagellum. A few short forms, concerning certain of which 

 some doubt existed as to whether or not there was a free flagellum, spicule 

 forms, were met with in both strains B and C. These, however, may be 

 neglected, as at least an equal number of short forms with a questionable free 

 flagellum is seen in T. evansi, which is recognised as the type of the 

 trypanosomes constituting Group 1 in Laveran's classification. 



In Table II are given the dimensions of the trypanosomes of each of the 

 three strains in rats and guinea-pigs. But little assistance in the differentia- 

 tion of the strains is to be obtained from these figures. It is to be noted that 

 in each case the average dimensions of the parasites in the rat are greater than 

 those of the same strain in guinea-pigs. This difference, which is but slight 

 in Strains B and C, is more marked in the case of Strain A. 



H 2 



