This question may sound silly, or at least redundant. But how on earth did Jonas Salk discover the Polio vaccine in the 1950’s?
Viruses are Submicroscopic. So you certainly can’t see them, at least with an ordinary microscope. How did he know when he rendered it inert, so he could safely inject it into people? Did he actually have to see the viruses? Or did he know the eureka moment some other way?
As I said, some people will say who knows, or who cares. But think about it. I will bet they didn’t even have an electron microscope back then. And I know the study of viruses, if not just the knowledge of them, must have been in its infancy.
You can see the effects of viruses on cells in tissue culture - you see that cells exposed to live virus die, while cells exposed to dead viruses survive, or the effects on animals susceptible to the disease. SeeHistory of polio vaccination
Generally, viruses were originally discovered as “infective agents” that were able to pass filters with pose sizes too small to allow bacteria to pass. To isolate them, one would apply various separation procedures on tissue extract, and test which fractions were able to either cause the disease in experimental animals or to infect susceptible cells in culture. You do not need to see the virus to do this.
Of course, the word “pose” was an autocorrect fail for “pores”, in case that wasn’t clear.
As an aside, the [URL=“Chamberland filter - Wikipedia”]use of such tiny pores](History of polio vaccination - PMC) to filter viruses from cellular life led to a mistaken assumption that all viruses are tiny. It was only as recently as 2003 that it was discovered that some viruses can be bigger than the smallest bacteria. (None of which are yet known to directly infect humans, but one was discovered infecting amoebas infecting humans (on a bump on a log in a hole in the bottom of the sea.))
I think your question is based on a more general misconception. All of cellular and molecular biology has been worked out with painstaking carefully-controlled experiments in which one element is varied/removed at a time, so that we can infer its role.
Visualizing structure can further elucidate function, but it is usually supplementary. We generally don’t figure out (or attempt to prove) how molecules interact by looking at them.
He used methods that would kill the virus. It must have been much scarier to produce the weakened live virus vaccine.
Incidentally, you can see viruses in an electron microscope. I used to work for a man who studied the T-series bacteriophages, which infected bacteria (E. coli).
I see that they tested the virus in test tubes containing live human cells. … A suitable mix of oxygenated water, salts and glucose and the cells can be kept alive… and even reproduce (like a cancer) so they could make endless amounts of the same exact same cell …
I think that if the virus is there, all the cells die.
So you could be sure the salk vaccine was dead, by testing it on test tubes of human cells that would show the virus was alive… put the vaccine in the set A of test tubes, put small samples of cultures of the live virus in set B of test tubes, and be sure that the difference is that the Salk vaccine does not cause polio virus, while the live virus does, in the same conditions…
Sabin… well they might be able to tell by the time taken to kill all the cells that the attenuated virus was weak against human cells.
Salk is safer for the individual, Sabin is more effective overall. The USA chose to vaccinate half its population with sabin even when most of them had salk … because salk wasn’t sure to wipe out polio but sabin is.
As others have stated, Salk didn’t need to see the viruses in order to study their effects. But just to correct this, Wikipedia says the first prototype electron microscope was built in 1931, and the first commercially available electron microscope was sold in 1938.
Uhm, we do, actually… but being able to do it requires the use of rules which were defined through observation. First we figure out “these things… (molecules or otherwise)… behave like This, whereas theseothers do not”; later, we find out what is different between these and theseothers; we hypothesize which of the observed differences are relevant; and we test by using test targets which have some of those differences but not others.
And while there are some properties which are relatively easy to figure out (which parts of a molecule will be reductors and which will be oxidizers, for example), to know the exact extent we still need experimentation and there are some properties which are much more complicated (how will a molecule interact with another molecule is much easier than how will it interact with a living being).
Not at all. Viruses had been discovered and named more than a half century earlier, and had been seen microscopically more than 15 years earlier. Viruses and their behavior were quite well known by the 1950s.
Pasteur developed a treatment for rabies in 1885 without being able to identify the causative agent. He speculated it was too small to be seen in microscopes. It was later understood that some infectious agents could pass through the finest filters for bacteria. The first virus to be identified as such was the Tobacco Leaf Mosaic Virus by Beijerink, who coined the word “virus” for such agents 1898.
Electron microscopy was invented in 1931 and the first images of viruses were obtained a few years later. Their structure was also studied by X-ray diffraction.
How does that work? When the host virus infects an actual cell, the parasite virus’s genetic code gets copied instead of the host virus’s? So the parasite virus can’t actually get into a cell itself, but it can get into another virus that can get into a cell?
Haven’t thought of that for decades…