In 1901, Leo Loeb1 published an account of the cultivation of epithelial cells from the guinea-pig embryo. He embedded bits of epithelium in solidified blocks of agar or serum and then planted these in subcutaneous pockets of adult guinea-pigs, from which they were excised at stated intervals, embedded in celloidin and sectioned serially. He thus used the adult pig as a living incubator of constant temperature with a constant flow of fresh sterile nourishment. He found that epithelium can grow without the presence of connective or other tissue, but in the absence of connective tissue, epithelial growth seems to be self-limited with no development of normal formations.
The first reports of the cultivation of animal tissues outside of the body were those made by R. G. Harrison2 in 1907 and again in 1910. He cultivated successfully bits of nervous tissue, using the excised medullary folds from early frog
SMYTH HF. THE CULTIVATION OF TISSUE CELLS IN VITRO AND ITS PRACTICAL APPLICATION. JAMA. 1914;LXII(18):1377-1381. doi:10.1001/jama.1914.02560430007004