ON THE PHOSPHORUS CONTENT OF THE 

 PARANUCLEIN FROM CASEIN.* 



BY HOLMES C. JACKSON. 



WHEN casein is treated with pepsin-hydrochloric acid, there 

 usually results an insoluble substance which has received 

 attention from a number of investigators. Lubavinf pre- 

 sented the first careful study of this product, which had 

 previously been described by Meissner under the name of 

 dyspeptone. He pointed out that the substance contained 

 organic phosphorus to the extent of 4.6 per cent, the latter 

 varying according to the conditions under which the digestive 

 experiments were carried out. 



In 1888 Chittenden4 while engaged in the study of the 

 digestive products of casein, carried out a series of analyses of 

 the insoluble residue corresponding to Lubavin's dyspeptone. 

 His preparations contained an average content of phosphorus 

 amounting to 2.57 per cent. It was pointed out, however, 

 that in every case the phosphorus found in the ash of the 

 products analyzed was as great as the total phosphorus ob- 

 served and Chittenden arrived at the conclusion " that instead 

 of being a phosphorized compound, it (dyspeptone) apparently 

 contains no phosphorus whatsoever, other than that combined 

 with calcium." Particularly noticeable in all his preparations 

 is the large percentage of ash, varying from 12.4 per cent to as 

 high as 15.4 per cent. On the other hand, it may be pointed 

 out that there is a rather striking constancy in the quantity 

 of phosphorus found in these preparations, the significance of 

 which will be referred to later. Chittenden was furthermore 



* Reprinted from the Amer. Jour, of Physiol. vol. iv. 



t Lubavin, Hoppe-Seyler*8 medicinisch-chemische Untersuchungen, 1871, 

 iv, p. 463. 



t Chittenden, Studies in Physiological Chemistry, Yale University, 1889, 

 iii, p. 66. 



