VII BONE 313 



tain no air, but are permeated with the nutritive fluid. 

 Each lacuna moreovei", at all events in young bone, 

 contains a nucleated cell, which is altogether similar in 

 essential character to a connective tissue or cartUage 

 corpuscle, and if the term were not already misused 

 might be called a "bone corpuscle." In fact, in 

 ultimate analysis the essential character of bone shows it- 

 self to be this : that it is a tissue analogous to cartilage and 

 connective tissue in so far as it consists of cells separated 

 by much intercellular substance ; and that it differs from 

 them mainly in the fact that calcareous matter is deposited 

 in and associated with the intercellular substance in such 

 a way as to leave minute uncalcitied passages (the canali- 

 culi), which open into the larger uncalcified intervals (the 

 lacu)ice\ in the neighboui-hood of the cells. 



The function of these passages is doubtless to allow of 

 a more thorough permeation of the calcified tissue by the 

 nutritive. fluids than could take place if the calcareous 

 deposit were continuous, and it is probable that, in an 

 ordinary bone, there is no particle Ifi square which is not 

 thus brought within reach of a minute streamlet of 

 nutritive plasma. 



This circumstance enables us to understand that which 

 one would hardly suspect from the appearance of a bone, 

 namely, that, throughout life, or, at all events, in early 

 life, its tissue is the seat of an extremely active vital 

 process. The permanence and apparent passivity of the 

 bone are merely the algebraical summation of the contrary 

 processes of destruction and reproduction which are 

 going on in it. 



If a young pig is fed with madder, its bones will be 

 found after a time to be dyed red. The madder dye, in 

 fact, getting into the blood, permanently dyes the tissue 

 with which it meets in its course through the bones. But 

 if the pig is fed for a time with madder, and is 

 then deprived of it, the amount of colour to be found in 

 the bones depends on the time which elapses before the 



