174 DISEASES OP THE HOKSE. 



ened, so that body or limbs must necessarily present double, and 

 natural delivery is rendered impossible. The bent neck may some- 

 times be straightened after the muscles have been cut on the side to 

 which it is turned, and the bent limbs after the tendons on the back 

 of the shank bone have been cut across. Failing to accomplish this, 

 the next resort is embryotomy. 



Tumors or diseased growths may form on any part of the foal, 

 internal or external, and by their size impede or hinder parturition. 

 In some cases what appears as a tumor is an imprisoned and undevel- 

 oped ovum, which has grafted itself on the fetus. These are usually 

 sacculated, and may contain skin, hair, muscle, bone, and other natural 

 tissues. The only course to be pursued in such cases is to excise the 

 tumor, or, if this is not feasible, to perform embryotomy, 



MONSTROSITIES. 



Monstrosity in the foal is an occasional cause of difficult parturi- 

 tion, especially such monsters as show excessive development of some 

 part of the body, a displacement or distortion of parts, or a redun- 

 dancy of parts, as in double monsters. Monsters may be divided 

 into — 



(1) Monsters with absence of parts — absence of head, limb, or 

 other organ. 



(2) Monsters with some part abnormally small — dwarfed head, 

 limb, trunk, etc. 



(3) Monsters through unnatural division of parts^-cleft head, 

 trunk, limbs, etc. 



(4) Monsters through absence of natural divisions — absence of 

 mouth, nose, eyes, anus, confluent digits, etc. 



(5) Monsters through fusion of parts — one central eye, one nasal 

 opening, etc. 



(6) Monsters through abnormal position or form of parts — curved 

 spine, face, limb, etc. 



(7) Monsters through excess of formation — enormous head, super- 

 numerary digits, etc. 



(8) Monsters through imperfect differentiation of sexual organs-^ 

 hermaphrodites. 



(9) Double monsters — double-headed, double-bodied, extra limbs, 

 etc. 



Causes. — The causes of monstrosities appear to be very varied. 

 Some monstrosities, like extra digits, absence of horns or tail, etc., 

 run in families and are produced almost as certainly as color or form. 

 Others are associated with too close breeding, the powers of symmet- 



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