58 R- J- Anderson, 



It is developed owing to changes attending on formation of limbs, it 

 is present in lowest vertebrates and results from the fusion of two 

 vessels, as two carotids in Python unite to form one. Osseous vari- 

 ations again are of small significance. Local suppression of a vertebra 

 or a part of one or excessive growth of a part may be the cause. 

 If vertebrae become few in one region, they do not necessarily in- 

 crease in number in some other region. Several causes may conjoin, 

 the coccyx and sacrum fuse and caudal vertebrae atrophy as the 

 pelvis is fixed with the erect attitude. Increase or diminution of the 

 cavities (and viscera) is responsible for increase or diminution of the 

 thoracic and abdominal vertebral -regions, and separation or approxi- 

 mation in the region of attachment of ribs. Variations occur in the 

 attachment of the limbs in Birds, Eeptiles and Fishes. The atavistic 

 theory with reference to the attachment of limbs is denied by some. 

 Anatomical variations seem to indicate some physiological disturbance, 

 especially in the district in which they occur. Just as the altered 

 social conditions in the manufacturing town of Dundee lead to a large 

 increase in the excess of marriageable females over marriageable males, 

 which is 2 per thousand all over Scotland, and 78 per thousand excess 

 in Dundee, so structures in human Anatomy show a tendency to vary 

 in response to altered conditions. 



Professor Eichard J. Anderson referred to the fact noticed by 

 Professor W. Krause and Professor Testut- that variations were rare 

 in animals as compared with man. When one sees how much Human 

 Beings are influenced in gesture and feature by the contemplation of 

 other animals it is not surprising that structural variations of a more 

 or less considerable nature should be constantly coming or going: 

 Take a Horse-Trainer, his success in his profession depends very largely 

 on his power to respond to every twitch the horse may give. Such 

 attention as he requires to exercise will tend to the bringing into 

 operation of certain muscle strands and to the throwing into rest of 

 certain others. For a generation or two the effects may continue and 

 then disappear. Then again man is the only Mammal that has much 

 power to imitate. There are probably few animals that man cannot 

 imitate in voice or gesture. He will compare with many birds in 



