2. Ivan Sechenov (1829–1905)
Ilya Repin/Tretyakov Gallery
“Medicine hardly is a science… we know nothing of the genesis of diseases, we don’t know why exactly some treatment helps or not,” a young and perplexed medical student Ivan Sechenov wrote in his diary in 1850. He was right – in the 19th-century doctors knew how to treat diseases but not what caused them. After becoming a scholar, Sechenov became the one to change it.
He studied in Germany, conducted long-term experiments, and became the first Russian specialist in physiology, giving the discipline the serious scientific basis it lacked. His fundamental work Reflexes of the Brain remains a milestone in neuroscience and the study of reflexes. Back in his day, conservative officials attacked Sechenov for undermining the concept of a God-given human soul, but time proved him right; today his authority is unquestioned.
, any of several unrelated snakes named for their reddish head colour. The North American copperhead Agkistrodon (also spelled Ancistrodon) contortrix is a venomous species found in swampy, rocky, and wooded regions of the eastern and central United States. Also called highland moccasin, it is a member of the viper family (Viperidae) and is placed in the subfamily Crotalinae (pit vipers) because it has the characteristic small, sensory pit between each eye and nostril. It is usually less than 1 metre (3.28 feet) long and is a pinkish or reddish snake with a copper-coloured head and reddish brown, often hourglass-shaped, crossbands on its back. It takes both cold- and warm-blooded prey and is important in rodent control. Many snakebites by it have been reported, but the venom of this snake is relatively weak and rarely fatal.
American crocodiles are more susceptible to cold weather than American alligators. American crocodiles do not have socials groups but occasionally, they congregate for feeding and basking in the daytime. While basking, they will leave their mouths wide open that exposes blood vessels in the mouth to cooler and warmer air, which helps regulate body temperature. While an American alligator can survive in water temperatures of 7.2 °C (45.0 °F) and below for some time, an American crocodile in that environment would lose consciousness and drown due to hypothermia. American crocodiles, however, have a faster growth rate than alligators, and are much more tolerant of saltwater.
American crocodile, Costa Rica
Unlike other crocodiles, the American crocodile use acoustic signals to communicate. Crocodile communication is centered on short-distance communications during courtship and hatching.