Vol. 6, 1920 PATHOLOGY: UNDERBILL, HONEIJ AND BOGERT 
79 
However, the fact that the fibers can form in a cell-free ground substance 
shows that no part of the cell cytoplasm is necessary for their differentia- 
tion from the ground substance. 
5. Any satisfactory theory of connective tissue formation must take 
into account the well-established fact that the great mass of the connec- 
tive tissues, both ground substance and fibers, is formed when not in con- 
tact with cells. The adherents of the intracellular theory of connective 
tissue formation, holding that both ground substance and fibers are living 
material, although of a different grade from that in cells, maintain that 
the embryonic connective tissue after it has been formed by an intracellular 
action has the power to grow through the assimilation of food material, and 
the ability to differentiate new fibers."^ 
6. The results of the present researches may be summarized as follows : 
(a) The origin of connective tissue lies in an intercellular secretion of 
the embryonic cells. This secretion constitutes the ground substance of 
the connective tissues and it increases in amount during development not 
by an assimilation of food materials and consequent growth but by the 
continued and additional secretions given off by the embryonic cells. 
(6) This ground substance secreted by the cells is of such a nature that, 
under the influence of various chemical and mechanical factors, it forms 
the connective tissue fibers by means of a consolidation of the minute 
elements of which it is composed in apparently the same way that a trans- 
formation of the plasma clot occurs. 
1 Baitsell, G. A., {a) J. Exper. Med., 21, 1915 (455); {h) Ibid., 23, 1916 (739); (c) 
Amer. J. Physiol., 44, 1917 (109). 
2 The presence of a primitive ground substance has been demonstrated by various 
investigators. E.g., see Merkel, F., Anat. Hefte, 38, 1908 (321); and Szily, A., Ibid., 
37, 1907 (649). Both of these articles contain a full review of the literature. 
3 Harrison, R. G., /. Exper. Zodl., 17, 1914 (521). 
^ E.g., see Heidenhain, M., Plasma und Zelle, pp. 33, 38, etc. 
CALCIUM AND MAGNESIUM METABOLISM IN CERTAIN 
DISEASES 
By Frank P. Underhii^l, James A. Honeij and L. Jean Bogert 
Laboratories oif Experimental Medicine and Radioi^ggy, School, of Medicine, 
YAI.E University 
Communicated by L. B. Mendel. Read before the Academy, November 10, 1919 
We wish to present some observations upon calcium and magnesium 
metabolism in leprosy and in multiple exostosis. 
Clinically, leprosy is characterized by a loss from the body of bone 
salts; in multiple exostosis bone salts are added to the organism for the 
calcification of the new growths. It is thus apparent that in these two 
abnormal conditions the processes involved in calcium and magnesium 
