174 THE KINGDOM OF MAN 



The protoplasm is drawn out at one end of the creature 

 into a motile undulating thread, and from the point 

 where this joins the body a membranous undulating crest 

 extends along the greater part of the animal's length. 

 There is no mouth, nutrition being effected by the 

 imbibition of soluble nutrient matter. 



After a long interval Gruby's trypanosome was re- 

 discovered in 1871 ; and then several kinds were described 

 in the blood of tortoises, fishes and birds. In 1878, Dr. 

 Timothy Lewis found a parasite in the blood of rats, at 

 first in India, and subsequently in the common rats of 

 London sewers. This parasite resembles a trypanosome 

 in many respects (fig. 46 A), but was very properly given 

 a distinct name by Savile Kent, who called it " Herpeto- 

 monas." This name has, however, been dropped ; and the 

 rat's-blood parasite is spoken of as a trypanosome. It is 

 the Trypanosoma Lewisii, and was the first of these 

 trypanosomes to be found in the blood of a mammalian 

 animal. The Trypanosoma Lewisii of the rat's blood 

 seems to do no harm to the rat, in which it swarms, 

 multiplying itself by longitudinal fission ; nor is it at 

 present known to produce any trouble in other animals 

 when transferred to their blood. Similarly, the frog's 

 trypanosome seems to exist innocently in the frog's 

 blood. 



The next trypanosome discovered (1880) was, however 

 found in the blood of camels, horses, and cattle suffering 

 from a deadly disease known in India by the name 

 " surra." It is called Trypanosoma Evansii, after the 

 observer who detected it. Trypanosomes now began to 

 get a bad name, for the next was discovered in animals 

 afflicted by a North African disease known to French 

 veterinaries as " dourine." This trypanosome was called 

 T. equiperdum. 



