472 MECHANICAL SEPARATION OF CELLULAR COMPONENTS 



ing the inside of the nickel vibrating element. Difficulty was expe- 

 rienced with separation of the parts of guinea pig sperm, since the 

 heads and tails come down at almost the same rate on centrifugation 

 giving fractions containing 12-15% of the unwanted portion in the 

 most successful cases. The contamination found in fractions from 

 other sources falls in the range of 1-4%. It is easy to obtain the 

 heads from human sperm since the tails are entirely dispersed by 

 the vibrations; however, a small part of the midpiece tends to re- 

 main with the head. The sonic treatment resulted in sc loss of the 

 acrosome from only the guinea pig sperm. 



Claude (1942) succeeded in separating granules of melanin from 

 the liver of Amphiuma tridactylum by alternate centrifugations of 

 3 min. at 18,000 times gravity and 1 min. at 1500 times gravity. The 

 granules were elongated, having dimensions of approximately 1 X 

 0.5 [x. A small proportion of melanin granules was found in guinea pig 

 liver, and they bore a striking resemblance to those separated from 

 the amphibian liver. 



