PAPERS ON BIOLOGY AND AGRICULTURE 111 



THE ANATOMY OF A DOUBLE MONSTER PIG 

 George M. Higgins, Knox College 



INTRODUCTION 



The literature upon various teratological forms is 

 rather extensive; and of the cases reported, syncephaly 

 is quite frequent. Fisher ( '04) in his Teratology Hand- 

 book records about 80 cases of syncephaly among domes- 

 tic animals and 50 cases within the human family. Since 

 that time additional records of a similar condition have 

 been made. Carey ( '17) described a case of syncephalus 

 asymmetros in a pig in which two distinct cerebro-spinal 

 axes were present and two hearts of unequal size in dis- 

 tinct pericardia, thus differing from any other case pre- 

 viously described. William and Rauch ( '17) likewise 

 described a case of syncephaly, also in a pig, in which the 

 heart was single, but the nervous system was fused to a 

 much greater degree, the spinal cords alone being dupli- 

 cated. 



This dissection of another syncephalous pig is pre- 

 sented because it is somewhat intermediate between those 

 mentioned above. In the but partial fusion of the brain, 

 the independence of the corpora quadrigemina, cerebel- 

 lar hemispheres and medulla, as well as in certain other 

 peculiar modifications of the anatomy, the writer feels 

 that publication is justifiable. 



This pig was presented to Professor George W. Hun- 

 ter of the Knox Biological Laboratory in October, 1922, 

 by the farmer upon whose farm the pig had been born. 

 The writer was assisted by Professor Hunter in the 

 earlier dissection, and acknowledgements are made for 

 this assistance as well as valuable suggestions through- 

 out the entire dissection. 



EXTERNAL ANATOMY 



This monster, one of a litter of six pigs, was born alive 

 but died at birth. It has a normal head with eyes, ears, 

 nares and snout in proper positions and proportions. 

 In the mid-dorsal line of the occipital region an addi- 

 tional pair of external ears of normal size are fused at 

 their bases around a single auditory aperture, which 



