Polarity in Organic Elements. 367 



but also in the greater development of the ridges and processes for mus- 

 cular attachment to them. The bones of the skull also accommodate 

 themselves to the brain within, growing when required, to make more 

 room. Sometimes it appears the growth is not sufficiently rapid from 

 the edges of the sutures to keep the gaps closed up ; in which case 

 there may be an independent growth of small bones inserted in the su- 

 tures. These are called " wormiana ossa, " from Wormius who described 

 them. They are not found in base of the skull, but chiefly in the lamb- 

 doidal, sagittal and squamous sutures. If the brain decreases in size 

 the skull accommodatingly thickens on its internal surface by the pro- 

 cess called " concentric hypertrophy. " 



The excessive development of the involuntary muscles which some- 

 times takes place is usually, if not always, referable to extra work put 

 upon them. ' ' Thus an extraordinary hypertrophy of the muscular coat 

 of the urinary bladder is often seen as a consequence of the obstruction 

 to the exit of the urine in consequence of a stone in the bladder or a 

 stricture in the urethra, so again hypertrophy of the muscular coat of 

 the gall bladder may take place in consequence of obstruction of its 

 duct by a gall-stone. Hypertrophy of the muscular coat of any part of 

 the alimentary canal may be induced by the existence of a stricture 

 lower down, and even hypertrophy of the heart is generally, if not al- 

 ways, attributable to obstruction to the exit of the blood which it pro- 

 pels, resulting either from stagnation of the pulmonary circulation by 

 the deficient aeration consequent upon disease of the lungs ( in which 

 case the hypertrophy is limited to the right side of the heart ), or from 

 the thickening or induration of the semilunar valves, or from narrowing 

 of the orfices of the aorta and pulmonary arter} T . " (Carpenter.) All 

 this extra growth of the parts is due to extra work and strain put upon 

 them to meet the demands of their accustomed functions. 



Tumors are to be considered as due to a species of hypertrophy, since 

 they constitute an excessive formation of matter properly belonging to 

 the parts to which they are attached. A tumor of the uterus, for ex- 

 ample, is made up of an excess of its normal ordinary tissues, but form- 

 ing a new organ out of them. This new organ, not having been devel- 

 oped in any sort of working relation with the other parts, is not limited 

 by them as they limit each other. But it may excite the growth or 

 hypertrophy of the uterus in the same way that its growth is excited 

 by its normal contents when pregnant, and the uterus may thus acquire 

 the power, under this stimulus, of sufficient contraction to separate and 

 expel the tumor, as in an act of parturition. 



Atrophy, the opposite of hypertrophy, is caused by want of nourish- 

 ment supplied to the part, regardless of the cause to which such defi- 

 ciency is due. A certain degree of activity is essential to keep any 



