HOOKWORM. 245 



these worms not only cause anaemia by the amount of blood 

 they actually consume, but when through feeding the point 

 of puncture they have made continues to bleed. This is sup- 

 posed to be due to the fact that they are provided with a 

 secretion which they utilize when feeding, and which prevents 

 the coagulation of blood. It is also believed that the toxins 

 they must excrete are responsible for the debilitating symp- 

 toms. One individual may harbor hundreds of these worms. 

 When uncinariasis, or hookworm disease, is suspected, the diag- 

 nosis may be made by an examination of the faeces. A small 

 piece of solid matter is mixed on a slide with water and exam- 

 ined with a 16 rn.m. objective and No. I eye-piece. The ova, 

 if present, will be seen as oval, highly refractile bodies, meas- 

 uring from 40-60 <>. in length. They are distinguished by 

 their oval shape and the paleness of their protoplasm, and by 

 the fact that there is nearly always a clean space between the 

 ectosarc and endosarc. The ova of the Old AVorld hookworm 

 are larger than those of the necator. In case of a negative 

 examination, small bits of the faeces should be mixed thoroughly 

 with saline or calcium chloride solution and centrifuged. This 

 washing and centrifuging should be repeated two or three 

 times and the washed sediment examined as before. Very 

 often ova which are few in number will be detected in this 

 way. 



QUESTIONS. 



What are the most common intestinal parasites which may be found in 

 man ? 



Describe the Ascaris lumbricoides. Its ova. How may infection take' 

 place ? 



' Describe the Oxyuris vermicularis. Its ova. What is the distinguishing 

 characteristic of its ova? How may infection take place? 



Describe the Trichocephalns dispar. Its ova. How may these be recog- 

 nized? 



What are the three principal varieties of Taenia? 



Describe the Tjenia saginata. Its ova. 



Describe the Tsenia sol mm. Its ova. 



Describe the Bothrioccphalus. Its ova. 



Describe the Taenia nana. Its ova. 



In what different animals do these worms have a life-cycle? 



What are Cystercerci ? 



Describe the Tamia echinococcus. 



Describe the Trichina spiralis. 



Describe the Necator americauus, or New World hookworm. 



