Phospho-nuclease. 



23 



soluble residue in the lower intestine. After parathyroidectomy 1 

 absorption and excretion were very low. The Ca content of the 

 blood however increased slightly which has been shown for P 

 also by Greenwald. 2 There is decreased P catabolism but increase 

 in the blood and Ca deprivation of tissues due to impaired ex- 

 cretion. Hyperthyroidism with its nervous symptoms would 

 represent increased catabolism with more normal excretion. 

 The apparent opposition of thyroid and parathyroid is likewise 

 explained by greater catabolism in presence of thyroid than in 

 absence of both. 



These facts and a host of others related to endocrinous gland 

 function may be interpreted briefly as follows. The intestinal 

 epithelium and leucocytes invading it (probably the splanchnic 

 basophiles) by virtue of the phosphonuclease they contain liberate 

 from nucleic acid (possibly other phosphoric esters also) phos- 

 phoric acid which dissolves Ca phosphate. Ca is carried partly in 

 combination with the leucocytes and is necessary for nucleolytic 

 action. Macallum 3 has shown these cells to absorb and transport 

 iron salts. Westbrook found the cells in extremely large numbers 

 in villi of carnivora, particularly the dog (bone ingestion?). 4 In 

 decalcification of bone the osteoclasts act in a similar manner. 

 In ossification the osteoblasts split off acid Ca phosphate which 

 hydrolyzes to the carbono-phosphate. 



The question as to why only certain tissues as cartilage calcify 

 is a distinct problem but may be largely a matter of chemotaxis. 

 As cartilage seems to have a specific adsorption affinity for Ca 

 salts and as Ca salts introduced from without stimulate ossi- 

 fication, Ca salts are probably the agents of the chemotaxis. 

 Likewise in pathological calcification, degeneration with liberation 

 of phosphoric acid in the tissue would lead to primary deposition 

 which would be continued by the leucocytes. Calcification in 

 the embryo chick must be analogous. 



The parathyroid must act by stimulating these processes as 

 instanced by parathyroid hyperplasia with osteomalacia and 

 atrophy with rickets, infantilism, osteitis deformans. Interesting 



1 Bergeim, Stewart and Hawk, J. Exp. Med., XX, 225, 1914. 

 1 Greenwald, J. Biol. Chem., XIV, 363, 369, 1913. 



3 Macallum, Jour. Physiol., 16, 268, 1894. 



4 Westbrook, /. Physiol., 18, 490, 1895. 



