chambers in the case of multiple births. it is reported that between 1504 and 1507, he experimented with the brain of an ox by injecting a tube into the ventricular cavities, injecting hot wax, and scraping off the brain leaving a cast of the ventricles. da vinci's efforts proved to be very helpful in the study of the brains ventricular system. da vinci gained an understanding of what was happening mechanically under the skin to better portray the body through art. for example, he removed the facial skin of the cadaver to more closely observe and draw the detailed muscles that move the lips to obtain a holistic understanding of that system. he also conducted a thorough study of the foot and ankle that continues to be consistent with current clinical theories and practice. his work with the shoulder also mirrors modern understanding of its movement and functions, utilizing a mechanical description likening it to ropes and pulleys. he also was one of the first to study neuroanatomy and made great advances regarding the understanding of the anatomy of the eye, optic nerves and the spine but unfortunately his later discovered notes were disorganized and difficult to decipher due to his practice of reverse script writing (mirror writing). for centuries artists have used their knowledge gleaned from the study of anatomy and the use of cadavers to better present a more accurate and lively representation of the human body in their artwork and mostly in paintings. it is thought that michelangelo and/or raphael may have also conducted dissections. importance in science study of the human skull by leonardo da vincistudy of the human embryo by leonardo da vinci cadavers are used in many different facets throughout the scientific community. one important aspect of cadavers use for science is that they have provided science with a vast amount of information dealing with the anatomy of the human body. cadavers allowed scientists to investigate the human body on a deeper level which resulted in identification of certain body parts and organs. two greek scientists, herophilus of chalcedon and erasistratus of ceos were the first to use cadavers in the third century b.c. through the dissection of cadavers, herophilus made multiple discoveries concerning the anatomy of the human body, including the difference between the four ventricles within the brain, identification of seven pairs of cranial nerves, the difference between sensory and motor nerves, and the discovery of the cornea, retina and choroid coat within the eye. herophilus also discovered the valves within a human heart while erasistratus identified their function by testing the irreversibility of the blood flow through the valves. erasistratus also discovered and distinguished between many details within the veins and arteries of the human body. herophilus later provides descriptions of the human liver, the pancreas, and the male and female reproductive systems due to the dissection of the human body. cadavers allowed herophilus to determine that the womb in which fetus’ grow and develop in is not bicameral. this goes against the original notion of the womb in which was thought to have two chambers; however, herophilus discovered the womb to only have one chamber. herophilus also discovered the ovaries, the broad ligaments and the tubes within the female reproductive system. during this time period, cadavers were one of the only ways to develop an understanding of the anatomy of the human body. galen (130–201 ad) connected the famous works of aristotle and other greek physicians to his understanding of the human body. galenic anatomy and physiology were considered to be the most prominent methods to teach when dealing with the study of the human body during this time period. andreas vesalius (1514–1564), known as the father of modern human anatomy, based his knowledge off of galen's findings and his own dissection of human cadavers. vesalius performed multiple dissections on cadavers for medical students to recognize and understand how the interior body parts of a human being worked. cadavers also helped vesalius discredit previous notions of work published by the greek physician galen dealing with certain functions of the brain and human body. vesalius concluded that galen never did use cadavers in order to gain a proper understanding of human anatomy but instead used previous knowledge from his predecessors. importance in medical field in the present day, cadavers are used within medicine and surgery to further knowledge on human gross anatomy. surgeons have dissected and examined cadavers before surgical procedures on living patients to identify any possible deviations within the surgical area of interest. new types of surgical procedures can lead to numerous obstacles involved within the procedure which can be eliminated through prior knowledge from the dissection of a cadaver. cadavers not only provide medical students and doctors knowledge about the different functions of the human body, but they also provide multiple causes of malfunction within the human body. galen (250 ad), a greek physician, was one of the first to associate events that occurred during a human's life with the internal ramifications found later after death. a simple autopsy of a cadaver can help determine origins of deadly diseases or disorders. autopsies also can provide information on how certain drugs or procedures have been effective within the cadaver and how humans respond to certain injuries. two procedures that have been practiced on cadavers include appendectomy and cricothyrotomy. appendectomies, the removal of the appendix, are performed 28,000 times a year in the united states and are still practiced on human cadavers and not with technology simulations. cricothyrotomy can also be successfully practiced on cadavers due to the high fidelity nature of the tissue. this presents an ideal situation for practicing a high-risk procedure that many clinicians report anxiety around performing. gross anatomy, a common course in medical school studying the visual structures of the body, gives students the opportunity to have a hands-on learning environment. the need for cadavers has also grown outside of academic programs for research. organizations like science care and the anatomy gifts registry help send bodies where they are needed most. preserving for use in dissection for a cadaver to be viable and ideal for anatomical study and dissection, the body must be refrigerated or the preservation process must begin within 24 hours of death. this preservation may be accomplished by embalming using a mixture of embalming fluids, or with a relatively new method called plastination. both methods have advantages and disadvantages in regards to preparing bodies for anatomical dissection in the educational setting. embalming with fluids emperor pedro ii of brazil lying in repose in 1891. he was embalmed on the day of his death. during the process, six liters of hydrochloride of zinc and aluminum was injected into his common carotid artery. in 1912, brazilian educator and archivist luís gastão d'escragnolle dória went to the emperor's glass-topped coffin. at the occasion, he had noticed the well-preserved state of pedro ii's body. the practice of embalming via chemical fluids has been used for centuries. the main objectives of this form of preservation are to keep the body from decomposing, help the tissues retain their color and softness, prevent both biological and environmental hazards, and preserve the anatomical structures in their natural forms. this is accomplished with a variety of chemical substances that can be separated generally into groups by their purposes. disinfectants are used to kill any potential microbes. preservatives are used to halt the action of decomposing organisms, deprive these organisms of nutrition, and alter chemical structures in the body to prevent decomposition. various modifying agents are used to maintain the moisture, ph, and osmotic properties of the tissues along with anticoagulants to keep blood from clotting within the cardiovascular system. other chemicals may also be used to keep the tissue from carrying displeasing odors or particularly unnatural colors. embalming practice has changed a great deal in the last few hundred years. modern embalming for anatomical purposes no longer includes evisceration, as this disrupts the organs in ways that would be disadvantageous for the study of anatomy. as with the mixtures of chemicals, embalmers practicing today can use different methods for introducing fluids into the cadaver. fluid can be injected into the arterial system (typically through the carotid or femoral arteries), the main body cavities, under the skin, or the cadaver can be introduced to fluids at the outer surface of the skin via immersion. different embalming services use different types and ratios of fluids, but typical embalming chemicals include formaldehyde, phenol, methanol, and glycerin. these fluids are combined in varying ratios depending on the source, but are generally also mixed with large amounts of water. chemicals and their roles in embalming embalmer at work formaldehyde is very widely used in the process of embalming. it is a fixative, and kills bacteria, fungus, and insects. it prevents decay by keeping decomposing microorganisms from surviving on and in the cadaver. it also cures the tissues it is used in so that they cannot serve as nutrients for these organisms. while formaldehyde is a good antiseptic, it has certain disadvantages as well. when used in embalming, it causes blood to clot and tissues to harden, it turns the skin gray, and its fumes are both malodorous and toxic if inhaled. however, its abilities to prevent decay and tan tissue without ruining its structural integrity have led to its continued widespread use to this day. phenol is a disinfectant that functions as an antibacterial and antifungal agent. it prevents the growth of mold in its liquefied form. its disinfectant qualities rely on its ability to denature proteins and dismantle cell walls, but this unfortunately has the added side effect of drying tissues and occasionally results in a degree of discoloration. methanol is an additive with disinfectant properties. it helps regulate the osmotic balance of the embalming fluid, and it is a decent antirefrigerant. it has been noted to be acutely toxic to humans. glycerin is a wetting agent that preserves liquid in the tissues of the cadaver. while it is not itself a true disinfectant, mixing it with formaldehyde greatly increases the effectiveness of formaldehyde's disinfectant properties. advantages and disadvantages of using traditionally embalmed cadavers the use of traditionally embalmed cadavers is and has been the standard for medical education. many medical and dental institutions still show a preference for these today, even with the advent of more advanced technology like digital models or synthetic cadavers. cadavers embalmed with fluid do present a greater health risk to anatomists than these other methods as some of the chemicals used in the embalming process are toxic, and imperfectly embalmed cadavers may carry a risk of infection. plastination gunther von hagens gunther von hagens invented plastination at heidelberg university in heidelberg, germany in 1977. this method of cadaver preservation involves the replacement of fluid and soluble lipids in a body with plastics. the resulting preserved bodies are called plastinates. whole-body plastination begins with much the same method as traditional embalming; a mixture of embalming fluids and water are pumped through the cadaver via arterial injection. after this step is complete, the anatomist may choose to dissect parts of the body to expose particular anatomical structures for study. after any desired dissection is completed, the cadaver is submerged in acetone. the acetone draws the moisture and soluble fats from the body and flows in to replace them. the cadaver is then placed in a bath of the plastic or resin of the practitioner's choice and the step known as forced impregnation begins. the bath generates a vacuum that causes acetone to vaporize, drawing the plastic or resin into the cells as it leaves. once this is done the cadaver is positioned, the plastic inside it is cured, and the specimen is ready for use. advantages and disadvantages of using plastinates plastinates are advantageous in the study of anatomy as they provide durable, non-toxic specimens that are easy to store. however, they still have not truly gained ground against the traditionally embalmed cadaver. plastinated cadavers are not accessible for some institutions, some educators believe the experience gained during embalmed cadaver dissection is more valuable, and some simply do not have the resources to acquire or use plastinates. body snatching railings used to protect graves from body snatchers while many cadavers were murderers provided by the state, few of these