114 TIMOTHY RICHARDS LEWIS. 



what spindle-shaped body, about ll^uin length, and with a some- 

 what thick flagellum about double this length, so that the total 

 length of the protozoon would be 33/x, something more than half 

 the length of the flagellated organism found in the rat's blood. 

 Near the base of the flagellum of Biitschli^'s protozoon a con- 

 tractile vacuole could be distinguished, but I have not been able 

 to detect any such vacuole in these rat-hsematozoa. 



Seeing that the blood of such a large proportion of rats con- 

 tains these organisms, I can hardly su2)pose that their existence 

 has hitherto escaped notice, unless it be that rats in Europe do 

 uot harbour like parasites, Davaine,i [[^ ^^\^Q recent edition of 

 his work, makes mention that M. Chaussat had found minute ne- 

 matodes in the blood of a black rat (Mtis raitus), but I have not 

 seen any nematode in the blood of rats in this country. In the 

 tissues, bladder, &c., of rats such parasites are very common, 

 but their description does not come within the province of this 

 paper. 



The nearest approach to the flagellated hsematozoa of rats 

 which I have seen described is to be found in a foot-note in 

 Dr. Bastian's ' Beginnings of Life,' ^ where it is stated that 

 Dr. Gros had seen minute worms {vermicides) in the blood of a 

 field-mouse {muloi) which were so numerous as to cause the 

 blood to present an animated appearance ; and that the blood 

 of the mole was often found to be in a similar condition. They 

 were so small as to be barely visible under a power magnifying 

 400 diameters. I have not been able to obtain any minute 

 description of these vermicules, but I anticipate that it will be 

 found that they closely resemble the flagellated protozoa found 

 in the blood of Indian rats. 



With regard to the health of the rats in which these flagel- 

 lated organisms were detected, there was nothing to suggest in 

 any way that they were less healthy than others not so afl'ected, 

 and I have repeatedly kept rats for a considerable time for the 

 purpose of observing whether any special symptoms would be 

 manifested suggestive of the existence of such organisms in the 

 circulation. It should be mentioned that it frequently happened 

 that the rats caught in a particular room would be afl'ected, 

 whereas the blood of rats in another part of the building would 

 not contain them. The servants had ultimately come to recog- 

 nize this, as, whenever they learnt that a particular rat's blood 

 contained the desired organisms, they dihgently endeavoured to 

 secure the rest of the family. 



Calcutta, August, 1878. 



» 'Traite ties Entoznaiies,' Edit, ii, pp. 11, 957; 1877. Letickart's 

 ' Parasiten,' vol. ii, p. 636. " Vol. ii, p. 338; 1872. 



