74 



DISEASES OF THE DIGESTIVE APPARATUS. 



Imperforate Anus. 

 {Atresia Ani.) 



This is a congenital deformity, and consists of a defective forma- 

 tion of the rectum and in some cases of the lower bowel. It is 

 sometimes seen in newly born puppies, and it is usually confined 

 to the cutaneous covering growing over the anus. It can be cut 

 with a small knife and the edge of the wound sewed back so as 

 to prevent it uniting again ; but if it is found that the lower bowel 

 is entirely occluded, it is better to destroy the puppy. 



INTESTINAL PARASITES. 

 (Helminthiasis. ) 



Round "Worms. [Asoaris Mystax.) 



Natural History. The round worm of the dog is white or 

 yellowish-white in color, and twisted in spirals; there is a differ- 

 ence in the two sexes (see Fig. 21): the males are about 45 to 



Fig. 21. 



Asoaris mystax : a, male ; b, female ; i;, head. 



60 mm., and the females from 102 to 130 mm. Their thickness 

 varies from 1 to 1.7 mm. The head is slightly flattened and 

 fitted with two wing-shaped borders, which start from the mouth 

 and enlarge slightly as they pass posteriorly. The mouth is a 



