132 SCIENCE PROGRESS. 



nucleic acid remained in solution and was obtained by 

 adding hydrochloric acid up to 0*3 per cent, and then 

 throwing it into an equal volume of alcohol containing the 

 same amount of hydrochloric acid when the acid was pre- 

 cipitated. He also obtained similar bodies from thymus 

 and egg-yolk. He showed that they all contained phos- 

 phorus varying in amount from 7*9 per cent, to 9/5 per 

 cent, and that sulphur was absent if the acid had been 

 completely separated from all proteid. 



Nucleic acid as thus prepared was found to be a white 

 amorphous powder giving a strong acid reaction. It dis- 

 solves fairly readily in water and very readily if a little 

 ammonia or other alkali be added. From this solution it 

 is not precipitated by an excess of acetic acid but is by 

 weak hydrochloric, especially in the presence of alcohol. It 

 is quite insoluble in alcohol and ether. 



As early as 1874 Miescher 1 described the preparation 

 and properties of a substance rich in phosphorus and of 

 marked acid properties which he had obtained from the 

 nuclei of salmon spermatozoa. This substance Miescher 

 regarded as a nuclein, but as was pointed out by Kossel he 

 was in reality dealing with nucleic acid. In his later work, 

 collected and published by Schmiedeberg 2 after the author's 

 death, Miescher recognises this and gives his further work 

 upon the chemistry of the acid. Nucleic acid is particularly 

 characterised by its instability and Miescher points out two 

 great dangers which have to be avoided if we wish to obtain 

 a preparation of unaltered nucleic acid. In the process of 

 purification it is extremely liable to decompose, with the re- 

 sult that it loses a considerable part of its phosphorus. In 

 the second place it is most easily split up in another manner 

 in which it loses a considerable part of its nitrogen which is 

 given off in the form of the so-called nuclein bases or allox- 

 uric bodies, xanthin, hypoxanthin, etc. This latter de- 

 composition occurs especially during that part of the prepar- 

 ation when it is necessary to employ dilute mineral acids, 



^Miescher: Verhandl. d. naturf. Ges. in Basel, Bd. 6, S. 138, 1874, 

 and Ber. d. d. chem. Ges., Bd. 7, S. 17 14, 1874. 



2 Miescher: Arch. f. exp. Path. 11. Phar?n., Bd. 37, S. 100, 1896. 



