SECTION XVI 



MALFORMATIONS 



]\Ialforinations among birds are occasionally observed. A 

 complete discussion of the dozens of various forms of mal-' 

 formations that may be found cannot be given here for lack 

 of space, but a few facts will be given. 



In higher animal life, including man, malformations have 

 been attributed to the following causes : 



External mechanical influences, such as falls, blows, or 

 severe shock of any kind, by affecting the general health of 

 the pregnant female, may have power to arrest, retard, or 

 otherwise disturb the normal development of the embryo or 

 fetus. 



The so-called spontaneous amputation, in utero, by a coil 

 of the umbilical cord finding its way around a part of the 

 fetus and causing 

 pressure and am- 

 putation, cannot 

 hold with chickens 

 nor will acute and 

 chronic placentitis, 

 causing adhesions, 

 hardly hold for 

 birds. 



The percentage 

 f malformations 

 in the human fam- 

 ily is one to three 

 or four thousand 

 births; in the low- 

 er animals and 

 birds the percent- 

 age is much small- 

 er. 



During the for- 

 mation of the fetus 

 an arrest of devel- 

 opment of the bud which forms the wmg may result in a mal- 

 formed wing; the same can be said of any other part, as the 

 leg, beak, etc. 



If the arrcDujcmoit of the groups of cells during develop- 

 ment does not follow the normal type, then malformations, as 



Fig. 72. Monster Chick (dipygus tetrabkachium.^ 



Showing two bodies, four legs, fcur wings and one 

 head. 



