y8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



outgrowths is shown by the very niany whose blood and lymph are 

 known to carry such poisons for years, without any effect on the ears. 

 Moreover, such poisons, when present, reach all parts of the osseous 

 system, yet produce nothing resembling the hyperostoses and exostoses 

 of the ear. The case for the internal poisons therefore is not a strong 

 one. 



There remains the factor termed conveniently " predisposition ". 

 This predisposition must be something limited to the external meatus, 

 for barring rare exceptions, no such bony growths appear elsew^here 

 on the skeleton. But what is the " predisposition "? It can hardly be 

 anything in the mechanics or the structure of the bone — if it were, 

 there would probably be other examples of such a condition and its 

 results elsewhere. There is no evidence that the tympanic bone is 

 unfinished or proliferating in spots. Yet the fault, essentially, can only 

 be with the meatus, or with what controls its structure and being. 



If the condition of ear exostoses is, as it appears to be, of the nature 

 of an osteogenic derangement, then it would be reasonable to regard 

 it as the result of a disturbed or weakened trophic control of the parts 

 aft'ected. The development of every part of the body is under a very 

 definite and heredity-bound neuro-vascular control. In the apes and 

 lower forms such control of the external bony meatus is evidently 

 thoroughly established and fully adequate. In man this control ap- 

 pears to be disturbed and no longer wholly sufficient ; and with, or 

 even without, sufficient exciting causes abnormal bony growths in the 

 ears are the result. Such a disturbance or weakening could possibly 

 be an accompaniment of the unprecedentedly great and rapid evolution 

 of tlie human head. Such radical change must have disturbed pre- 

 existing trophic controls, and a full reaccommodation has not yet been 

 reached, at least not in most of the human groups. 



Another, though related, way would be to look upon the deranged 

 neuro-vascular control of the external aural canal as an expression of 

 degeneration. Degeneration may be defined as a generalized, progres- 

 sive groupal insufficiency of the organism to sustain the developmental 

 level reached by an organ. Such insufficiency can again only be based 

 on inadequacy of the trophic nerve centers. It differs diametrically 

 from the inadequacy of accommodation in that it tends to augment 

 with time, whereas the latter tends to diminish, unless the evolutionary 

 changes that caused it keep on advancing. 



Can the osteogenic disturbance which results in ear exostoses be 

 regarded as a process referable to a pan-human greater or lesser de- 

 generative condition of the tympanic bone or the external meatus? 



