POPULAR MISCELLANY. 



713 



in favor of the girls. Voluntary motor abil- 

 ity is measured by the number of taps the 

 child can make in five seconds. The average 

 child at six years taps 20 - 8 times in that in- 

 terval. From this there is a gradual increase 

 till the age of twelve, when the rate is 29 - 9 

 taps. This is lowered one tap at thirteen 

 after which the increase is resumed and 

 reaches a maximum at seventeen, when the 

 rate of tapping is 33'8 in five seconds. The 

 rate is higher for boys than for girls. After 

 tapping for forty-five seconds fatigue enters 

 into the results very noticeably. The fa- 

 tigue is most marked at the age of eight and 

 least marked at fifteen. Boys tire more 

 quickly throughout in voluntary movement 

 than girls, but as they act more vigorously it 

 can hardly be said that they tire more easily. 

 Boys have a larger lung capacity than girls 

 throughout. Girls become nearly stationary 

 in it at twelve, but boys do not begin their 

 most rapid growth till they are fourteen years 

 of age. The time of simple reaction de- 

 creases with age. The results, when consid- 

 ered for girls and boys separately, show 

 marked differences in sex. The bright chil- 

 dren react more quickly than the dull. But 

 all react in about the same time just before 

 those ages eleven and sixteen in which 

 changes of growth manifest themselves. In 

 the test for reaction with discrimination and 

 choice, ability increased and the length of 

 time required decreased with advance in age. 

 This test implies more complicated mental 

 activity, and the influences that affect mental 

 life show themselves more plainly in the 

 curve representing such development. 



Uses of the Sand Blast. It appears from 

 an account of the applications of the sand 

 blast given by Mr. J. J. Holtzapffel, in the 

 English Society of Arts, that glass is almost 

 immediately depolished by the blasts now in 

 use, and only a little time is required to 

 pierce and cut holes through sheet and plate 

 glass. Stone, marble, slate, and granite are 

 equally amenable to its action. Iron, steel, 

 and other metals have their surfaces easily 

 reduced and smoothly or coarsely granulated, 

 according to the force and abrasive powder 

 used. The abrasive need not be harder than 

 the metal to which it is applied. The blast 

 is used for frosting and decorating glass, the 

 labeling of graduated measures, for remov- 



ing hard scale from castings and forgings, for 

 carvings and inscriptions in intaglio or relief 

 on stone, slate, and granite, for delicate draw- 

 ings for lithography, for removing fur and 

 deposits in tubs and tanks, for cleaning off 

 accumulations of paint and dirt within iron 

 ships, for decorating buttons, for piercing 

 the holes in glass ventilators, for marking 

 pottery and ornamental tiles, for refacing 

 grindstones, emery and corundum wheels, for 

 granulating celluloid films for photography, 

 and on wood to bring out the grain in relief, 

 and, latterly, for blocks for printing. 



Tnberenlosis in Meat. The Koyal Com- 

 mission appointed in July, 1890, to inquire 

 into the effect of food derived from tubercu- 

 lous animals on human health has reported, 

 as the result of its five years' investigations, 

 that it has obtained ample evidence that 

 " food derived from tuberculous animals can 

 produce tuberculosis in healthy animals. The 

 proportion of animals contracting tuberculo- 

 sis after experimental use of such food is 

 different in one and another class of animals ; 

 both carnivora and herbivora are susceptible, 

 and the proportion is high in pigs. In the 

 absence of direct experiments on human sub- 

 jects we infer that man also can acquire 

 tuberculosis by feeding upon materials de- 

 rived from tuberculous food animals. The 

 actual amount of tuberculous disease among 

 certain classes of food animals is so large 

 as to afford to man frequent occasions for 

 contracting tuberculous disease through his 

 food." The commission thinks it probable 

 that an appreciable part of the tuberculosis 

 that affects man is obtained through the 

 food. Tuberculous disease is observed most 

 frequently in cattle and in swine. It is 

 found far more frequently in full-grown cat- 

 tle than in calves, and with much greater 

 frequency in cows kept in town cowhouses 

 than in cattle bred for the express purpose 

 of slaughter. It is but seldom found in the 

 meat substance, but principally in the organs, 

 membranes, and glands. It is found in the 

 milk of cows when the udder has been at- 

 tacked by tuberculous disease, and seldom 

 or never when the udder is not diseased. In 

 the milk it is exceptionally active in its oper- 

 ation upon animals fed either with the milk 

 or with dairy produce derived from it. Pro- 

 vided every part that is the seat of tubercu- 



