INFUSORIA. 231 



These flagellates are generally considered harmless, although doubt as to this is 

 expressed by some authors. 



Lamblia. 



Lamblia intestinalis. These parasites are aboutioX i5/* and have a pear-shaped 

 body with a depression at the blunt anterior end. This depression enables the 

 flagellate to attach itself to the summit of an epithelial cell. Around the depression 

 are three pairs of flagella which are constantly in motion. Another pair of flagella 

 project from either side of the blunt little tail-like projection. When stained, the 

 parasites have a pyriform shape with two chromatin staining areas on either side 

 of the anterior end. When encysted, they assume an oval shape. This parasite 

 is generally considered as of little importance, but inasmuch as, when in great num- 

 bers in the caecum and appendix, they may give rise to symptoms resembling appen- 

 dicitis and as they are responsible for a chronic and intractable diarrhoea associated 

 with mental and physical depression, this is undoubtedly an affection only minor in 

 importance to amoebic infection. It is a common infection in the tropics. 



INFUSORIA (CILIATA). 



The Infusoria are the most highly developed of the Protozoa. 



The bodies of Infusoria are oval and may be free or attached to a stalk-like 

 contractile pedicle, as with Vorticella, or they may be sessile. The cilia, which are 

 characteristic, may be markedly developed around the cytostome (mouth) and serve 

 the purpose of directing food into the interior, while others act as locomotor organs. 

 The body is enveloped by a cuticle which may only have one opening or slit, to serve 

 as mouth; or it may have a second one, a cytopyge or anus. Usually the faecal 

 matter is ejected through a pore which may be visible only when in use. They usu- 

 ally have a large nucleus and a small one. Infusoria tend to encyst when conditions 

 are unfavorable (as when water dries up in a pond). When the cilia are evenly 

 distributed over the entire body of the ciliates we have the order Holotricha; when 

 ciliated all over, but with more prominent cilia surrounding the peristome, we call 

 the order Heterotricha. It is to this order that the Infusoria of man belong. 



Balantidium coli. -This is the only ciliate of importance in man. 

 It is a common parasite of hogs. It is from 60 to ioo/i long by 50 to 

 'jofJ. broad, and has a peristome at its anterior end which becomes narrow 

 as it passes backward. It has an anus. The ectosarc and the endosarc 

 are distinctly marked. The cuticle is longitudinally striated. 



These parasites cause an affection similar to dysentery and may bring about a 

 fatal termination. It is almost impossible to escape noticing the actively moving 

 bodies if a faecal examination is made. When encysted they are round. 



Another ciliate, the B. minimum, 25 x 15^, has also been reported for man. 



Nyctotherus faba has a kidney-shaped body and is about 25 by 15;*. It has a 

 large contractile vacuole at the posterior end. It has a large nucleus in the center 

 with a small fusiform micronucleus lying close to it. It has only been reported 

 once for man. 



