PHOSPHOROUS SUBSTANCES OF THE CELL. 133 



and though Miescher showed that it was easy to prevent the 

 loss of any of the phosphorus, it was much more difficult to 

 prevent the loss of any of the nitrogen. To avoid the latter 

 source of error he found that it was necessary to keep the 

 temperature of all solutions down to o° C, the whole time of 

 the preparation, and particularly during the treatment with 

 dilute acid, the time of which it is further necessary to re- 

 duce to the lowest possible limit. His method is to take 

 the ripe spermatozoa and rub them up in water. The 

 emulsion is then strained through a cloth, precipitated by 

 adding a few drops of acetic acid, and filtered. The pre- 

 cipitate is washed thoroughly with alcohol and ether to re- 

 move fats, lecithin, etc., and then thoroughly shaken with 

 0*5 per cent, hydrochloric acid and this extraction repeated 

 four or five times. It is in the later extractions that the 

 danger of splitting off some of the nuclein bases is especially 

 incurred. The residue is next dissolved in £ per cent, soda, 

 filtered, and the filtrate acidified with hydrochloric acid 

 when the nucleic acid is partially precipitated, but only 

 completely on the addition of two volumes of alcohol. 

 During the whole of these processes the preparation and all 

 reagents added are cooled down to about o° C. A general 

 and striking reaction given by nucleic acid is that in acid 

 solutions it will precipitate proteids, producing bodies which, 

 as Altmann showed, very closely resemble if they are not 

 identical with the nucleins obtainable from most tissues. 



The importance of the part that nucleic acid plays in the 

 animal economy, either when united with proteid molecules 

 to form compound proteids or in a free state, stands forth 

 clearly when we study the nature of the decomposition pro- 

 ducts which have been obtained from it, or, on the other 

 hand, by a study of the positions from which it has been 

 obtained. Thus its distribution is found to be chiefly, if 

 not entirely, in the nuclei of cells. The chromatin of the 

 nuclei appears to be the chief source of the acid, as is seen 

 from Miescher's and other experiments in which the nuclei 

 have been isolated in quantity and found to consist almost 

 entirely of nucleic acid combined with a base, protamine. 

 This conclusion is further strengthened by a study of the 



