GROWTH, METAMORPHOSIS AND DEVELOPMENT 271 



tissue degeneration; in rickets we find quite the reverse, namely, 

 an over-production of the osteoplastic tissue, so that we lack the 

 conditions necessary to the precipitation of calcium phosphate and 

 carbonate, or, in other words, bone formation. 



Osteomalacia, bone consumption, is in certain respects the reverse 

 of rickets. If in rickets we find a deficient precipitation of insol- 

 uble lime salts, in osteomalacia we have the eating away of existing 

 bone. Osteomalacia occurs most frequently during pregnancy, dur- 

 ing which even under normal conditions the teeth may suffer. 

 Osteoporosis, the bone consumption of the aged, which is especially 

 noticeable in the skull, belongs to this group. Here, too, we must 

 reject the theory of the deficient introduction of lime salts, as it is 

 contradicted by all metabolism researches. We are much more in- 

 clined to accept a dissolving away of calcium phosphate and carbon- 

 ate, especially by acids. Since the oxidizing processes are deficient 

 and the circulation functionates less perfectly, an accumulation of 

 acids is not surprising. MAGNUS LEVY has raised the objection to 

 this "acid theory" that the proportion of the calcium phosphate to 

 calcium carbonate is the same in osteomalacic as in normal bones. 

 He placed normal bones in lactic acid and found that much more 

 carbonate than phosphate is dissolved away, and from this he con- 

 cluded that the "acid theory" was useless. This objection can- 

 not be allowed. If acid diffuses from any direction into a mixture 

 of calcium carbonate and phosphate imbedded in a jelly, the acid 

 advances only to the extent that it has previously dissolved away 

 all the carbonate and phosphate; this was shown experimentally 

 by R. LiESEGANG* 2 (assuming, of course, that an acid stronger than 

 phosphoric acid is employed). As may be readily seen, the result of 

 the experiment depends entirely upon the conditions; at any rate 

 the contribution of MAGNUS LEVY cannot count against the "acid 

 theory." 



Concrements. 



In various pathological processes we find in the body cavities of 

 animals and men, structures varying in size from that of a grain of 

 sand to that of a fist, and which have developed without the help of 

 cells. Such precipitates are called concrements. We find them as renal 

 gravel, urinary calculi, gallstones, brain sand (in the lymph spaces of 

 the brain), rice bodies in the exudate of diseased joints; as the pearl of 

 the pearl oyster; and similar formations which are found at times in 

 cocoanuts, in view of their structure, can be considered nothing else. 



The common characteristic of all concrements is that in addition 

 to the special characteristic ingredients (urates and cholesterin) they 



