“I observed certain animalcules, within whole bodies I saw so quick a motion as to exceed belief; they were about the size of a large grain of sand, and their bodies being transparent, that the internal motion could plainly be seen. Among other things, I saw in the body of one of these animalcules a bright and round corpuscle, placed near the head, and in which a very wonderful swift motion was to be seen, consisting of an alternate extension and contraction. This particle I concluded to be the heart.”
![“[The heart is] really a fascinating organ. It's about the only organ in the body that you can really witness its function. Doing things. And so on. Some of the other organs you can witness, like the intestines, will have this sort of peristaltic motion. But nothing that can compare with the…” quote by Denton Cooley](https://sms4smile.com/quotes/img-quotes/f48/denton-cooley-33225_activity_the-heart-is-really-a-fascinating-organ_1120230.jpg)
![“Very often conditions are recorded as observable "under thy fingers" [...] Among such observations it is important to notice that the pulsations of the human heart are observed.” quote by James Henry Breasted](https://sms4smile.com/quotes/img-quotes/e9a/james-henry-breasted-20001_anatomy_very-often-conditions-are-recorded-as-ob_1436000.jpg)
![“I've spent more time than many will believe [making microscopic observations], but I've done them with joy, and I've taken no notice those who have said why take so much trouble and what good is it?” quote by Antonie van Leeuwenhoek](https://sms4smile.com/quotes/img-quotes/5b8/antonie-van-leeuwenhoek-17943_believe_i-ve-spent-more-time-than-many-will-beli_560375.jpg)
![“The 4th sort of creatures... which moved through the 3 former sorts, were incredibly small, and so small in my eye that I judged, that if 100 of them lay [stretched out] one by another, they would not equal the length of a grain of course Sand; and according to this estimate, ten hundred thousand…” quote by Antonie van Leeuwenhoek](https://sms4smile.com/quotes/img-quotes/9f1/antonie-van-leeuwenhoek-17943_bacteria_the-4th-sort-of-creatures-which-moved-th_627470.jpg)
