180 THE PROTEIN SUBSTANCES. 



which the barium salt, which is difficultly soluble in water, must be 

 mentioned. 



According to NEUMANN, the two thymus nucleic acids, a and /5, can 

 be obtained from the gland, after previously boiling the latter with water 

 containing acetic acid and then cutting it up fine. The finely divided 

 gland is boiled with about 3-per cent NaOH for one-half hour for the a-acid 

 and two hours for the /?-acid, and sodium acetate is added at the same 

 time. After neutralization with acetic acid, filtration and concentra- 

 tion, the product is precipitated with alcohol. The nucleic acids can 

 be obtained from the precipitated sodium nucleates by precipitating with 

 alcohol containing hydrochloric acid. In the separation of the two 

 acids, KOSTYTSCHEW makes use of the different behavior of the barium 

 salts on saturating their solution with barium acetate (see above). 

 LEVENE'S method consists, on the contrary, in treating the organs first 

 with 5-per cent sodium hydroxide or with 8-per cent ammonia in the cold, 

 then nearly neutralizing with acetic acid, precipitating the proteins with 

 picric acid, and treating the strongly acidified liquid (acetic acid) with 

 alcohol. In the presence of sufficient acetate the nucleic acids are pre- 

 cipitated. More recently LEVENE has suggested that the nucleic acid 

 be dissolved in strong acetic acid and then precipitated with copper 

 chloride or hydrochloric acid. SCHMIEDEBERG (in collaboration with 

 HERLANT) who has suggested a careful method for the preparation of 

 the nucleic acids as copper compounds, has recently l given very exact 

 and detailed instruction as to the preparation of the nucleic acids. In 

 regard to the details for the various methods of preparation we must 

 refer to the original publications cited below. 



Guanylic acid may be best prepared, according to BANG and RAAS- 

 CHOU, 2 by the following method: After treating the pancreas vvith 1- 

 per cent sodium-hydroxide solution for twenty-four hours at the room 

 temperature, it is dissolved by warming, then made faintly acid with 

 acetic acid, filtered, made faintly alkaline with ammonia, strongly con- 

 centrated, and precipitated with alcohol while hot. The proteoses 

 remain in solution, and the precipitated guanylic acid (-acid) is purified 

 by repeated solutions in water and precipitations by alcohol. 



In regard to the preparation of inosinic acid we refer to the works 

 of HAISER, of NEUBERG and BRAHN and of LEVENE and JACOBS cited on 

 page 179. 



Plant Nucleic Acids. Those best known are the yeast nucleic acid and the 

 triticonucleic acid, C 41 H 61 N ie P 4 O 3l , isolated by OSBORNE and HARRIS from the 

 wheat embryo, and which according to these investigators is identical with the 

 yeast nucleic acid. Yeast nucleic acid has the probable formula C 38 H 50 N 15 P 4 O 29 , 

 according to LEVENE. 3 Instead of Z-xylose it contains d-ribose as the pentose, 



1 Schmiedeberg, Arch. f. exp. Path. u. Pharm., 43 and 57; Herlant, ibid., 44; Neu- 

 mann, Arch. f. (Anat. u.) Physiol., 1899, Suppl.; Levene, Zeitschr. f. physiol.Chein., 

 32 and 45; Kostytschew, ibid., 39. 



2 Hofmeister's Beitrage, 4. 



3 Biochem. Zeitschr., 17. 



