ANIMAL MICRO-PABASITES. 599 



H^.MATOZOA OF E.ATS. 



In describing these organisms, Lewis remarked that it was- 

 strange that they had not occupied attention before, and suggested 

 as an explanation that possibly European rats did not harbour thes& 

 parasites. The author examined a few white rats, but without 

 success, and then proceeded to examine the blood of common brown 

 rats, trapped from the London sewers, and discovered that these- 

 oi'ganisms are to be found in no less than 25 per cent, of apparently 

 healthy animals. The first question which naturally arose was 

 whether these organisms in European rats were identical with those^ 

 dascribed by Lewis in Indian rats. 



If we refer to the description given by Lewis, we find that he 

 states that when he first noticed them he thought they were vibrios 

 or spirUla. The drop of blood 

 under examination appeared to 

 quiver with Hfe ; and on diluting 

 the blood, motile filaments could 

 be seen rushing through the 

 serum and tossing the blood- 

 corpuscles about in all directions. 



The filaments were pale and 

 translucent, without any trace 

 of visible structure or granu- 

 "larity, and they were more un- 

 dulatory in movement than ^^^_ 239.- Parasitbs in the Blooi> 

 spirilla. A corpuscle might be of Rats (Lewis), 



observed to quiver, and this 



could be distinctly traced to be due to the existence of a flagellum,. 

 apparently a posterior Jlagellum, as the organisms seemed generally 

 to move with the thicker end forward ; no fiagellum could be- 

 detected at the opposite end. The greater number of the figures- 

 in the woodcut (Fig. 239) are described as representing these- 

 organisms a few hours after the blood had been obtained, when 

 their movements are not so rapid, and the fiagellum becomes more 

 easily recognisable. 



This observation led Kent, who named the organism Herpetomonas: 

 Lewisi, to remark that if, as Lewis is inclined to maintain, that- 

 organ " propels instead of draws the animalcule through the in- 

 habited serum, we have presented a structural and functional feature 

 ■ without parallel among the other representatives of these Protozoa- 

 flagellata, the recognition of which would demand the creation of a 



