The early days of microscopy (before describing...) Flashcards
What were 4 early mentions of lenses?
Aristophanes in 424 BC - used a lens for a plot device in a play
Pliny in 1st century AD - used lenses for therapeutic burns and magnifying in water
Alhazen AD 962-1038 - enlarging images and retinas - a transparent sphere can produce enlarged images
Robert Grosseteste and Roger Bacon 13th century AD - telescopes, eyeglasses, burning lenses, magnifiers
When was the compound microscope officially invented?
1590 by Hans and Zacharias Janssen
Who officially invented the compound microscope?
Hans and Zacharias Janssen and Hans Lippershey
they weren’t credited until the 17th century
When did Galileo build his own compound microscope?
1609
What makes a compound microscope superior to one-lens magnifiers? what were its original downfalls?
better: having 2 lenses means higher magnification
worse: 2 lenses creates aberrations (inaccuracies/distortions) which make it hard to know what is real and what is a product of the lens
Why did some people object the compound microscope?
people distrusted the microscope because it was
unnatural to assist the human eye to see unknown things
misleading - to some extent it was cause of the distortions
what was the first organism to be drawn from magnifications by Francisco Stelluti?
in 1630 Stelluti drew bees from his observations
What were Robert Hooke’s early contributions with microscopes?
he was the Curator of the Royal Society in London in the 17th century and he set up microscope demonstrations every week for the meetings and collected observations in the Micrographia book
How did the microscope help finalize Harvey’s model of blood circulation?
Marcello Malphigi (1661) used microscopes to examine frog lungs and discovered the capillary connections between arteries and veins = a structural connection
this connection made it clear that blood flowed away from the heart via vessels and was not poured into empty spaces to be absorbed by the tissues
Who was Marcello Malphigi (c. 1661)? What were his major. contribiutions?
He made some important observations with microscopes in the 17th century
discovered the capillary connections between arteries and veins in frog lungs = Harvey’s model of blood circulation completed
observed embryological development in chickens through his microscope and ignited the debate of how biological form develops
Who started the debate about how biological form develops? Epigeneticists vs. preformationists?
Malpighi and his microscope studies on chicken embryological development
What view would an epigeneticist take on how biological form develops? What are epigenetics?
‘epi’ = on or above in Greek –> factors beyond the genetic code
modifications to the DNA that affect gene expression caused by external factors (environmental)
they would argue that biological form is not set in stone at embryonic stage and that external factors can influence development = form developed from formless
What view would a preformationist take on how biological form develops?
children are essentially tiny adults and that a tiny, fully formed human is implanted in the sperm or egg at conception and just grows in size
basically form is set in stone at conception
= development and growth were the same thing
Which of the 2 arguments, epigenetics or preformationism, predominated after the ignition of the debate of biological form development in 1660?
preformationist argument won out against epigenetics through the 18th century
Who was Antoni van Leeuwenhoek (1632-1723)? What were his major contributions?
a cloth merchant and amateur scientist
he was interested in science, inspired by Robert Hooke (Micrographia) and used magnifiers to examine fabrics = took up microscopy by building his own single lens, high powered microscopes (less aberrations)
T or F: Leeuwenhoek was a true scientist that went to university
false, he was a cloth merchant and AMATEUR scientist
What was significant about Leeuwenhoek’s microscopes?
they were one lens but high magnifying power (tiny lenses) - ~100-200x magnification and due to just being single lensed, they did not have the same aberrations and distortions of compound microscopes
How did Leeuwenhoek circulate his work since he wasn’t in a university circle?
he sent a lot (400) letters to the Royal Society of England for publication in their journal
What were Leeuwenhoek’s 4 major findings?
- blood and circulation - independently of Malpighi, he found presence of capillaries
- discovered microorganisms
- generative cells (sperm cells)
- disproved spontaneous generation
Who discovered and helped complete Harvey’s blood circulation idea?
both Malpighi (first) and Leeuwenhoek (unlearned) but independently of one another
How did Leeuwenhoek discover microorganisms?
with his high magnifying microscopes, he wanted to understand why some peppers were hot, he submerged them in water to look at samples and found tiny organisms (bacteria)
How did Leeuwenhoek discover generative cells?
he analyzed semen samples from a medical student’s patient with gonorrhea and observed tiny motile sperm cells
How did Leeuwenhoek disprove spontaneous generation?
he didn’t believe corn weevils could spontaneously form in stored corn so he studied the corn weevil life cycle with his microscope and found that they reproduce
When did the popularity of microscopy die off?
it kicked off in the 17th century, but died off in popularity in the early 19th century because:
became a ‘rich man’s toy’ - too expensive for the average scientist and also scientists didn’t want to be thought of as playing with toys, but taken seriously
quality of the equipment was poor and created distortions = distrust and unnatural
Leeuwenhoek also turned away prospective students
Why did the 19th century see the reemergence of microscopy?
lenses with fewer aberrations and clearer viewing were developed
coating was developed to enhance precision and magnification
