664 TEXTBOOK OF ZOOLOGY 



It is likely that this development is controlled by hormone relation- 

 ships, and it is in cases in which this balance is disturbed that 

 hermaphrodites occur. There is still much to be learned concerning 

 the causes of this condition. 



Cardiac Anomalies 



Transposition of the heart to the right side of the midline of the 

 body is known as dextrocardia and occurs rarely. It is usually 

 associated with displacement of other visceral organs. 



There has been a case reported recently in which the autopsy of 

 a 73-year-old farmer disclosed that he had died because of a rup- 

 tured left ventricle of an extra heart. One of the hearts of this 

 man was in the normal position, the other (the one that failed) was 

 located just above the spleen and below the left lung in the lower 

 part of the chest. The hearts were both of about normal propor- 

 tions and both functioned actively. They both joined the aorta. 



Due to faulty development, an incomplete interventricular septum 

 is occasionally found in the four-chambered hearts. The failure of 

 complete development of the septum between the auricles to close 

 the foramen ovale is a more common anomaly. It has been reported 

 that this occurs in some degree in one case in four for the human 

 being. Actual mixing of auricular blood sufficient to interfere with 

 normal function is much less common, however, because of the over- 

 lapping of the membranous walls which are pressed together by the 

 pressure of contraction. In a small number of human cases the 

 aerated blood and unaerated blood from the two auricles do mix 

 and produce a purplish colored blood and in turn affects the color 

 of the skin. Such a case is known as a ''hlue hahy" and often 

 leads to early death. 



Abnormalities of Brain and Sense Organs 



Encephalocoele is due to the protrusion of a sac of the meninges 

 and part of the brain through a defect in the roof of the cranium. 

 An abnormally large brain, which is usually associated with the 

 distention of the cranium by superabundance of cerebral fluid, is 

 known as hydrocephalus, or the size may be macrocephalus. The 

 opposite extreme in which the head and brain are abnonnally small 

 due to failure of development is known as micro cephalus. 



