108 THE GERM THEORY OF DISEASE. 



forming the secretion. But it is plain that other tissues are 

 not so protected, or, if so protected, that protection is in some 

 way withdrawn, under special circumstances. How? The 

 nerve force suggests itself; but this hypothesis presents serious 

 difficulties. It seems much more probable that the explana- 

 tion is to be found in the development of the power of form- 

 ing the soluble ferment, than in the withdrawal of the power 

 of resisting it. In all cases in which I have personally made 

 examination of the tissue advanced against resorbed surfaces, 

 surfaces being removed, I have found a marked change in the 

 general appearance of the tissue. It has taken on the appear- 

 ance, more or less, of granulating tissue, and these changed 

 cells have received the name of osteoclasts, odontoclasts, etc., 

 according to their location and purpose. The fact that this 

 peculiar development is the accompaniment of resorption of 

 bone, roots of teeth, etc., is universally recognized, I believe, 

 by histologists. The inference, then, that this solvent-form- 

 ing power is a special development, would seem to be main- 

 tained. We conclude that this special soluble ferment is only 

 formed under special circumstances. Physiologically, only 

 in case some tissue not wanted longer is to be removed ; as 

 bone during growth, and consequent change of form, roots of 

 temporary teeth at shedding time, or when some foreign 

 substance has been lodged in the tissue. Pathologically, 

 through some irritation or other abnormal condition, the tissue 

 is induced to a false action. We can understand that the pres- 

 ence of a substance, such as a catgut ligature or a sponge, 

 should induce some special action of the tissue, through which 

 it would be freed from its presence. But how the same 

 phenomena should be called into play for the removal of 

 parts of bone during growth, for the purpose of rendering 

 them symmetrical and perfecting their form, is more difficult 

 of comprehension. Take, for instance, the phenomena of the 



