_All Other Waters_. Total organic elements to .2 .2 to .4 Over .4 Oxygen required to .15 .15 to .2 " .2 Albuminoid ammonia to .010 .010 to .015 " .015 {185} In connection with impure water should be mentioned impure ice. Ice is purer than the water from which it forms, but if cut on a foul pond it will itself be foul, and the vitality of some microscopic organisms is not destroyed by their being frozen, as is shown by the fact that samples from the centre of blocks of ice will inoculate sterilized infusions with the germs of putrefaction, precisely as the water of which the ice is composed would have done before it was frozen. Disease has been traced to impure ice, and it may be that it is more frequently due to this cause than has heretofore been supposed; at all events, it is well to bear the possibility in mind. The subject of impure water will be further considered in speaking of habitations. IV. CLIMATE.--The literature of the effects of different climates upon the human body is very extensive, following the general rule that the less positive or precise knowledge there is upon a given subject the more will be written about it. Of all animals, man seems to adapt himself most readily to the extremes of climate; and, although it is commonly supposed that a tropical climate is injurious to those coming from cooler regions, yet it has been found that where he takes the same precautions to ensure cleanliness, pure water and air, and proper food, the European does not have a higher rate of mortality in Algeria or in the East or West Indies than he does at home, if the effects of cholera and yellow fever be excepted. Dr. Parkes defines the effect of climate upon the human body to be "the sum of the influences which are connected with the solar agencies, the soil, the air, or the water of a place;" in other words, he makes it nearly equivalent to the locality or the environment. By "climate" we understand, commonly, the sum of meteorological influences, the most important of which, as regards health, are temperature, humidity, and wind. The effects of temperature in producing disease are often confounded with the effects of change of temperature, which last is perhaps the more important of the two, and should be specially borne in mind in advising climato-therapy for chronic or wasting diseases.