Most ebook files are in PDF format, so you can easily read them using various software such as Foxit Reader or directly on the Google Chrome browser.
Some ebook files are released by publishers in other formats such as .awz, .mobi, .epub, .fb2, etc. You may need to install specific software to read these formats on mobile/PC, such as Calibre.
Please read the tutorial at this link: https://ebookbell.com/faq
We offer FREE conversion to the popular formats you request; however, this may take some time. Therefore, right after payment, please email us, and we will try to provide the service as quickly as possible.
For some exceptional file formats or broken links (if any), please refrain from opening any disputes. Instead, email us first, and we will try to assist within a maximum of 6 hours.
EbookBell Team
4.7
86 reviewsDuring phylogenesis, blood appears with the multicellular organisms called metazoans, where the majority of cells lose direct contact with the body surface. Cells are not able to accept oxygen and nutrients from the body surface and give away products of their metabolism. Therefore, the internal environment has developed. In vertebrates, there is vascular circulation (in a closed system of tubes) and lymphatic circulation. Blood enables exchange of substances between distant cellular populations and thus their specialization, regulation, etc. The circulation in humans is in one direction, of which the heart is the driving engine.