590 A MANUAL OF BACTERIOLOGY 



macronucleus, and a small or micronucleus or blepharoplast ; 

 the latter is not, as in the Infusoria, composed of generative 

 chromatin, and is in relation with the locomotor apparatus. An 

 undulating membrane, a thin protoplasmic membrane attached 

 to one aspect of the body like a dorsal fin, may be present. 

 Euglena is a common form in ditches, and Noctiluca is the chief 

 cause of phosphorescence in the sea ; both are uniflagellate. 

 V olvox and Protococcus are also placed by some in this group. 

 The chief parasitic genera are : 



Trypanosoma and Trypanoplasma, both of which? have an 

 undulating membrane, but the former has one flagellum, the 

 latter two flagella, one at each end of the body, but both starting 

 from the blepharoplast, which is situated at the non-flagellated 

 end of the body. 



Herpetomonas is like Trypanosoma, but has no undulating 

 membrane. The flagellum runs the length of the body. 



Leptomonas has a single flagellum starting from the end of the 

 body (Fig. 55, p. 598). 



Crithidia has a single flagellum and a short undulating mem- 

 brane running half the length of the body. 



The trypanosomes and other forms living in the blood-plasma 

 are known as hsemoflagellates. 



Trichomonas intestinalis l 



This is the commonest of all the intestinal parasites of man. It 

 inhabits the large intestine and caecum and may occur in enormous 

 numbers, though the infection does not seem to be of long duration, 

 and may quickly disappear. Ordinarily it appears to be quite 

 non-pathogenic, though Escomel in South America states that a 

 dysenteric condition may be induced by it. 



The organism has a pear-shaped body 5-15 /u, in length. At the 

 blunt anterior end a spherical nucleus is present, just anterior to 

 which is a chromatin granule from which three long free flagella 

 arise, which are directed forwards, and a fourth thicker flagellum 

 which passes backwards in a slightly spiral manner attached to the 

 border of an undulating membrane, beyond which it is continued 



1 On human intestinal proto/oa, see Wenyon, Lancet, 1915, vol. ii, p. 1 178 : 

 Wenyon and O'Connor, Human Intestinal Protozoa (Rale, Sons and Daniels- 

 son, 1917). 



