196 DISEASES OF THE HOESE. 



back. All this suggests the development of extra parts from the 

 same primary layer of the impregnated and developing ovum. The 

 eli'ect of disturbing conditions in giving such wrong directions to 

 the developmental forces is well shown in the experiments of St. 

 Hilaire and Valentine in varnishing, shaking, and otherwise break- 

 ing up the natural connections in eggs, and thereby determining the 

 formation of monstrosities at will. So, in the mammal, blows and 

 other injuries that detach the fetal membranes from the walls of. the 

 womb or that modify their circulation by inducing inflammation are 

 at times followed by the development of a monster. The excitement, 

 mental and physical, attendant on fright occasionally acts in a simi- 

 lar way, acting probably through the same channels. 



The monstrous forms liable to interfere with parturition are such 

 as, from contracted or twisted limbs or spine, must be presented 

 double: where supernumerary limbs, head, or body must approach 

 the passages with the natural ones; where a head or other member 

 has attained to an unnatural size; where the body of one fetus has 

 become inclosed in or attached to another, etc. 



Extraction is sometimes possible by straightening the members 

 and obtaining such a presentation as will reduce the presenting mass 

 to its smallest and most wedgelike dimensions. To effect this it 

 may be needful to cut the flexor tendons of bent limbs or the muscles 

 on the side of a twisted neck or body: one or more of the manipu- 

 lations necessary to secure and bring up a missing member may be 

 required. In most cases of monstrosity by excess, however, it is 

 needful to remove the superfluous parts, in which case the general 

 principles employed for embryotomy must be followed. The Ca'sa- 

 rean section, by which the fetus is extracted through an incision in 

 the walls of the abdomen and womb, is inadmissible, as it prac- 

 tically entails the sacrifice of the mare, which should never be done 

 for the sake of a monster. (See " Embryotomy,"' p. 202.) 



Entrance of twins into the passage at once. — Twins are rare in 

 the mare, and still more rare is the impaction of both at once into 

 the pelvis. The condition would be easily recognized by the fact 

 that two fore limbs and two hind would occupy the passage at once, 

 the front of the hoofs of the fore feet being turned upward and 

 those of the hind feet downward. If both belonged to one foal, they 

 would be turned in the same direction. Once recognized, the con- 

 dition is easily remedied by passing a rope with a running noose 

 round each foot of the foal that is furthest advanced or that prom- 

 ises to be most easily extracted, and to push the members of the 

 other fetus back into the depth of the womb. As soon as the one 

 fetus is fully engaged into the passage it will hold its place and its 

 delivery will proceed in the natural way. 



