We demonstrate the importance of measuring the mechanical properties of biological tissue in vivo by quantifying the mechanical properties of bovine vitreous both in its native state and upon removal from the eye. The mechanical properties are determined by the cavitation rheology technique developed in our labs to determine the linear modulus. This technique involves inducing a cavitation event at the tip of a syringe that is located at an arbitrary location within the vitreous sample. The pressure at which the cavitation event occurs can be directly related to the modulus. We show that the modulus decreases upon removal of the vitreous from the ocular cavity and decreases still further when the vitreous cortex, the thin membrane that surrounds the vitreous, is removed. This study has important implications for both diagnostic science of diseased tissue and developmental biology in studying tissue properties with age.