258 CONNECTIVE TISSUE. 



This, to some extent, is influenced by certain conditions for 

 example, on the skull-bones by the growth of the brain, both in 

 a progressive and regressive way (Virchow). The regression is 

 shown by the absorption in advancing age, producing the thin- 

 ning of the bones so characteristic of the senile skeleton. 



THE GROWTH AND RETROGRESSION OF BONE. 



In the light of my researches, continued for ten years, the 

 theory of an interstitial growth of the bone is no more tenable 

 than is the interstitial growth of any other tissue. Basis-sub- 

 stance, once formed, cannot increase in bulk by simple expansion. 

 The observation that the bone-corpuscles in the old are farther 

 separated than in the young is no proof of an interstitial growth, 

 since Steudener has demonstrated (see page 220) that the periph- 

 eral portion of each bone-corpuscle in advancing age is trans- 

 formed into basis-substance. New tissue forms exclusively from 

 embryonal or medullary tissue, and an already formed tissue must 

 return to its embryonal condition, by liquefaction of the basis- 

 substance, before a new tissue can arise. An augmentation of the 

 bulk of a tissue can take place only by new formation of the 

 living matter of the embryonal corpuscles, that is, an increase of 

 the number of the embryonal corpuscles. 



This law was first, though incompletely, established by H. 

 Miiller, in 1858 j it was asserted as to the growth of bone-tissue 

 by L. Ranvier in 1865, and announced to be a universal law for 

 all tissues by myself in 1873. The process of inflammation, first 

 accurately studied by S. Strieker, also illustrates the law. In- 

 flamed tissue, according to S. Strieker, returns first to its embry- 

 onal condition before new formation arises. 



We are indebted to A. Kolliker's accurate researches * for the 

 discovery that every growing bone on its surfaces exhibits regu- 

 larly recurring " planes of resorption " (Resorptions-flachen). The 

 bone to the naked eye looks rough, as if corroded ; under the 

 microscope the bone-tissue proves to be spongy, provided with 

 bay-like erosions or excavations, which, as a rule, contain multi- 

 nuclear bioplasson masses. Kolliker maintains that these bodies 

 are growing into the bone-tissue from without, and that they 

 actually absorb and destroy the bone structure. For this reason 



"Die Normale Resorption des Knochengewebes u. ihre Bedeutung fiir 

 die Entstehung der Typischen Knochenformen." Leipzig, 1873. 



