Ryder.] 550 [Xov. 1, 



A Physiological Theory of the Calcification of the Skeleton. 



By Prof. John A. Ryder. 



(Read before the American Philosophical Society, November 1, 1SS9.) 



The well-known researches of Harling, Rainey (1858), and Orel (1879) 

 on the interference exerted by the physical properties of colloids in modi- 

 fying the form of crystalline bodies left to crystallize therein, may 

 alTord the basis for an interpretation of the processes attending the gene- 

 sis of the calcareous skeleton in many living forms. Especially is this 

 true if we keep in view the significance of the indifferent intercellular 

 colloids normally produced at certain places in the living organism, and 

 their comparative passivity with reference to all of the metabolic pro- 

 cesses going on in the surrounding active or cellular tissues. The sub- 

 stances which, when isolated, as Collagen, Elastin, Chondrigen, Chon- 

 drin, etc., represent in a separate form the basis of the non-cellular, 

 passive and supporting structures or skeletal elements which serve as 

 points of attachment for the apparatus of motion, the muscular system. 

 These materials, which are essentially of intercellular origin, represent 

 the colloidal or fibro-laminar matrix of bone and cartilage throughout the 

 vertebrates, in which calcareous matters are thrown down and retained, 

 so as to give more or less firmness or rigidity ; or, as a firm jelly, as in the 

 case of cartilage, in which cells are imbedded, a certain rigidity is at- 

 tained through the molecular .stability and cohesion of the structures so 

 formed, as in bars of cartilage, for example. 



The one series of features which characterizes these bodies is their inter- 

 cellular orii;in, their homogeneity and molecular stability or inactivity. 

 They therefore stand in the most extreme contrast with respect to their 

 physical properties when the latter are compared with the other active, 

 living cellular tissues of the organized bodies in which they are found. 

 While all of the living cells of the organism exhibit an active metabolism, 

 the non-cellular supporting tissues, such as the white fibrous, yellow 

 elastic and cartilaginous, cannot of themselves exhibit anything of the 

 sort, but only through the intermediation of the vascular and other tissues 

 is such metabolism possible. Cartilage is usually not traversed by vessels. 

 and is never richly vascular, though it may give passage to a few widely 

 scattered vessels, as happens in some of the cranial cartilages of the stur- 

 geons. As a rule, the presence of vessels in cartilage carries the implica- 

 tion that they have grown into the cartilage secondarily ; myeloj^laxes or 

 or other aracebiform cells have eroded the cartilage in advance of the in- 

 growing vessel. In the highest types of bone development, as met with in 

 mammals, birds, reptiles and Amphibia, this is the way in which the carti- 

 lage is removed from the centres of long bones, after it has served its purpose 

 as a matrix upon which the forms of the permanent skeletal elements have 

 been moulded in the form of the firmer and more stable substance which 



