228 



ESSENTIALS OF ZOOLOGY 



The work of several embryologists seems to indicate that the pro- 

 duction of twins either as normal individuals or otherwise is re- 

 lated to this condition. 



Harelip and Cleft Palate 



These two defects are related and are sometimes found together. 

 The lateral palatine processes may fail to complete growth and 

 unite properl}^, thus leaving a gap in the roof of the mouth which 

 opens directly into the nasopharynx above. 



Fig. 68. — A case of harelip due to arrested development. 



Harelip (cheiloschisis) is a very common defect and is due to the 

 failure of union of the nasal and maxillary processes. There may 

 be double harelip or single harelip. In connection with double hare- 

 lip it sometimes happens that the premaxilla projects beyond the 

 outline of the face to form what is called luolf-snoiit. Harelips are 

 frequently remedied by a surgical operation early in life. 



Diaphragmatic Hernia (Open Diaphragm) 



An extreme case of this was found in a cat which was being used 

 for dissection purposes in Baylor University. The animal had lived 

 an apparently normal life and had been killed for laboratory study 

 without showing evidence of its abnormality until dissected. From 



