126 BOARD OF AGRICULTURE. 



For an adult the dose is four or five grains, twice a day, on 

 every second day, for a week, the quantity to be diminished if 

 the medicine causes ill effects, such as spasms, tenesmus, etc. 

 It often causes temporary perversion of vision, things appear- 

 ing of unnatural colors, etc., but this effect soon passes away. 



The root of male fern (see page 191), given in powder, in 

 connection with purgative medicines, is also recommended. 



As means of prevention, the use of impure water should be 

 avoided. And if water from streams and ponds must be 

 used for drinking, as in most large cities, it should be 

 thoroughly filtered through powdered charcoal. 



The Round-worm of the Horse (Ascaris megalocephala 

 Cloquet) . 



This species inhabits the intestine of the horse, ass, and 

 mule, and is quite common. It closely resembles the preced- 

 ing species in form and general appearance, but grows to a 

 larger size, the male becoming ten inches long, and the female 

 twelve inches or more. The mouth is surrounded by three 

 large, rounded, very prominent lobes or papilla. In the male 

 the tail is provided with wing-like folds along the sides ; in 

 the female it is conical, terminating in a point, the female 

 genital opening being situated in the anterior fourth of the 

 body. 



This species likewise produces vast numbers of eggs, which 

 develop embryos externally to the body, in water. Dr. Cob- 

 bold states that he has reared free, active embryos from these 

 eggs by keeping them five months in water. The horses, 

 most probably, swallow these embryos in the water that they 

 drink. 



These parasites, when numerous, will no doubt produce 

 effects analogous to those caused in the human body by the 

 preceding species, and the remedies will be similar. 



The Round-worm of the Cat (Ascaris mystaxRndolphi). 



Although very common in the cat, this parasite is of inter- 

 est chiefly on account of its occasional occurrence in the 

 human intestine. 



It may be easily distinguished by the presence of peculiar 



