International Comparisons of Medical Care
In the planning of health-care systems it would be useful to know if there are universal patterns in their use. Such patterns are sought in a survey of health care in 12 areas of seven countries...
Features
Giant Radio Galaxies
A powerful radio telescope in the Netherlands has revealed that energetic radio sources associated with galaxies are the largest obj ects known in the universe, extending millions of light-years...
How Bacteria Swim
The helical filaments of the thin flagella that propel bacteria do not wave or beat but instead rotate rigidly like propellers! And they are driven by a reversible rotary motor at their base...
The Causes of Biological Diversity
Within a single species individuals differ in many genetic traits, such as the chemical composition of their proteins. It appears that this diversity is actively maintained by natural selection...
The Perception of Surface Color
Colors are normally regarded in terms of wavelength and intensity. The colors of surfaces are much more complex. Consider the subtle variations of color in a blue scarf carelessly thrown on a table...
The Floor of the Mid-Atlantic Rift
Last summer U.S. and French submersibles explored a rugged area at some 8,400 feet where lava wells up and the ocean floor moves outward, bearing with it the continents to the east and the west...
A Pre-Columbian Urban Center on the Mississippi
About A.D. 1000 there arose In the area north and south of what is now St. Louis the most populous Indian settlements north of Mexico. Foremost among them was Cahokia, which included some 120 mounds...
The Stellar-Orientation System of a Migratory Bird
When the indigo bunting is put in a planetarium, it exhibits an ability to orient itself by the stars. This, howerer, can be only one of the cues it uses for long-distance narigation
Departments
50 and 100 Years Ago, August 1975
Science and the Citizen, August 1975
- Letters
Letters to the Editors, August 1975
- Recommended
Books, August 1975
- Mathematical Recreation
Mathematical Games, August 1975
- Amateur Scientist
The Amateur Scientist, August 1975
- Departments
The Authors, August 1975
Bibliography, August 1975
