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THE POPULAR SCIENCE MONTHLY. 



presence of others. Some substances, inor- 

 ganic or organic, when added to the solution, 

 are neutral ; others evolve the oxygen and 

 are themselves unchanged ; a third kind 

 evolve the oxygen, and with that some of 

 their own contained oxygen ; and a fourth 

 kind absorb the oxygen. Thus, with oxide 

 of iron there is no action ; with black oxide 

 of platinum a taper can be lighted from the 

 oxygen thrown off ; with permanganate the 

 action is very brisk, and oxygen is thrown off 

 from both substances; and arsenious acid 

 absorbs oxygen from the solution. Dr. Kich- 

 ardson has found peroxide of hydrogen use- 

 ful in a large number of diseases ; among 

 them are consumption, whooping-cough, ul- 

 cers and purulent exudation, syphilis, dia- 

 betes, ana3mia, rheumatism, and others, his 

 experiments with which, and his methods of 

 application, are described in a paper recently 

 read by him before the Medical Society of 

 London. 



Origin of Caste. — The origin of caste in 

 India was traced by General T. Dennehy, in the 

 International Oriental Congress, probably to 

 the contact of the Indo-Aryans on their first 

 migration with the uncouth, uncivilized abo- 

 rigines of the countries which they traversed. 

 The Aryans were even then highly civilized 

 and careful as to personal cleanliness and 

 religious observances, and naturally shrunk 

 against contact with the unwashed aborigi- 

 nes. They were particularly so with regard 

 to food, and hence arose the first manifesta- 

 tions of caste in the exclusion of strangers 

 from their meals. This custom grew with 

 years to be a cherished observance, and 

 what was first a measure of hygienic precau- 

 tion became an article of religious belief. 

 The later developments of caste corresponded 

 with the guilds of European countries so 

 prevalent in the middle ages. New castes 

 were seen growing up in India as new neces- 

 sities arose. For example, since the estab- 

 lishment of railroads it had been necessary 

 to find pointsmen (switchmen) and firemen; 

 and these men, being anxious to preserve 

 the emoluments of their posts in their own 

 families, were now actually crystallizing into 

 a new caste. The views expressed by M. 

 C. A. Fret, though differing from these, were 

 not inconsistent with them. He discerned 

 the working of evolution in caste. The Indo- 



Europeans formed at an early period a social 

 hierarchy which continued in full force long 

 after the language spoken by them had 

 ceased to be a living tongue. The general 

 ignorance prevailing in primitive times neces- 

 sarily involved the evolution of a priestly 

 or teaching caste — the Brahmins. The ne- 

 cessity of having men always on guard 

 against the attacks and invasions of neigh- 

 boring races with different tendencies led 

 to the warrior class or caste. These two 

 leading castes represented the two leading 

 principles in the constitution of civilization 

 — the religious and the military. The civil 

 principle, properly so called, did not come 

 into existence till a later period. 



Little Annoyances and Health.— Such 



matters as water supply, sewerage and drain- 

 age, streets and pavements, including means 

 of rapid transit, parks, and open spaces, 

 lighting, provisions for the dead and for 

 those affected with contagious disease, and 

 the sale of improper food and drinks, are 

 classed by Dr. John S. Billings, in his address 

 on Public Health and Municipal Government, 

 as variables under municipal control, many 

 of which have a powerful influence on the 

 health of the people. A large part of the 

 discussions as to the best way to arrange and 

 manage them, or as to whether in any par- 

 ticular place at a particular time the munici- 

 pality is doing its duty with regard to them, 

 turn on sickness and death-rates. It should 

 be borne in mind, however, Dr. Billings adds, 

 that no sharp dividing-line can be drawn 

 between comfort and health ; that there are 

 many things — such as noise, dust, offensive 

 odors, rough streets, etc. — the influence of 

 which upon sickness and death-rates it would 

 be at present difficult or impossible to demon- 

 strate, at least to the satisfaction of a court 

 of law, which yet add materially to the 

 burdens of life of those who are subjected 

 to them, and may in some instances turn the 

 scales between life and death. The human 

 body in some diseases may be likened to a 

 heavy railway train going up a very steep 

 grade. If the fire under the boiler can be 

 kept bright and clear, if the fuel and water 

 hold out, and the engineer is skilled and 

 careful to get the benefit of every pound of 

 steam power developed, then the train will 

 just reach the top of the hill, provided there 



