390 POPULAR SCIENCE MONTHLY. 



due to irritation of the terminal nerve filaments of the articular 

 nerves. 



M. Deroche thought he found that the muscular atrophy was 

 due to diminution of interfibrillary substance, and that there was 

 an ascending degeneration of the posterior columns on the same 

 side. However that may be, the inference is certainly justifiable 

 that massage acts to prevent muscular atrophy by maintaining 

 an influence, a movement, or something in the muscles which the 

 spinal cord is for a time unable to impart to them ; and in order 

 to do this, it should be applied immediately or soon after the 

 injury, for then it is more quickly aroused from the lethargy and 

 stupor into which it has been plunged by the shock of the acci- 

 dent. 



PEARLS AND MOTHER-OF-PEARL. 



By CHARLES STUART PRATT. 



A MONG the picturesque industrial possibilities of our south- 

 -j~ ern Pacific coast is the artificial production of pearls. By 

 this is meant, not the manufacture of artificial pearls, but the arti- 

 ficial growing of real pearls ; that is, instead of the haphazard 

 pearl-fishing of the present, the establishment, on the southern 

 California coast, of oyster ranches, where the pearl-producing 

 bivalves shall be scientifically directed and assisted in growing 

 both gem pearls and mother-of-pearl. 



This is hardly more visionary than was the recent establish- 

 ment of ostrich ranches just inland from this same Pacific coast. 

 A glance at the natural process of pearl-making will throw some 

 interesting light on these oyster ranches-to-be. Mother-of-pearl 

 is the natural product of the wild oyster, if we may so designate 

 the bivalve of the unf enced sea bottoms. To secure a smooth sur- 

 face for the contact of its soft, sensitive body, the oyster lines its 

 coarser, rougher shell with a substance named nacre which is 

 simply carbonate of lime, with a trace of organic matter. This 

 nacre is secreted and deposited in successive layers of filmy thin- 

 ness and of marvelous smoothness of surface ; the result is the 

 lustrous, iridescent motherof -pearl. 



Unlike mother-of-pearl, the gem pearl, round or otherwise, is 

 an imnatural product of the oyster. The gem pearl is an acci- 

 dent, almost a disaster, to its creator. In fact, a healthy, undis- 

 turbed oyster never produces a pearl. But if a sharp grain of 

 sand finds its way inside the shell, the disturbed oyster protects 

 its tender, sensitive flesh from the irritation of this offending sub- 

 stance by depositing about it smooth coatings of the nacre with 

 which it has already formed or deposited the mother-of-pearl 



