CALCIFICATION. 51 



quite in liarmonj with the fanction of the lymphatics as drains 

 for the removal of superfluous pabulum ; those points of the 

 parenchyma towards which the currents proceeding in every 

 direction from the capillaries converge, being furnished with 

 adequate means of drainage. I will show hereafter how this 

 digression may be brought to bear on the subject now in 

 hand ; at present I will only say that true bone is one of the 

 few tissues wdiich are absolutely devoid of lymphatics. 



Just as the limits of the individual vascular territories of 

 the young bone are marked out by calcareous infiltration, so the 

 bone, as a whole, is separated from the cartilage by a limitary 

 zone of tissue infiltrated with earthy salts, belonging half to the 

 cartilage and half to the bone ; it is this very zone of calcifica' 

 tion which has so long obscured our knowledge of the develop- 

 ment of bone. In strict accuracy we must consider this neutral 

 boundary as belonging, not to the bone proper, but to the sum 

 of the outermost medullary spaces which lie next the cartilage, 

 and are supplied by the terminal loops of the nutrient artery. 

 This is distinctly seen in that perversion of growth which con- 

 stitutes rickets. In this disease some of the terminal medul- 

 lary spaces of the bone penetrate fur into the proliferating layer 

 of the cartilage, which is of unusual breadth. The zone of 

 calcification is interrupted at many points ; and even Vircliow 

 remarked that to make up for this, little centres of calcification 

 are met with higher up in the substance of the cartilage, which 

 may be viewed as in some sort the membra disjecta of the cal- 

 careous zone. On makin<x a transverse section throuirh this 

 region, we may see how the entire mass of cartilage is partitioned 

 out into oval territories of unequal size by the said infiltration 

 of earthy salts, the middle of each territory being occupied 

 by one of the projecting medullary spaces alluded to above, with 

 its axial capillary loop. Here too, therefore, we find the cal- 

 careous infiltration mapping out the vascular territories, and 

 that in a tissue which possesses no trace of lymphatics either in these 

 ^' lines of contact" or in any other part of its substance (fig. 17). 



I consider myself fully justified in expressing the view, 

 founded on the above data derived from normal histology, that 

 peculiarities in the movement of the nutrient juices, and 

 especially a certain retardation, or even stagnation, of their 

 current, which may be assumed as likely in the said localities, 



