Abstract
Living cells are necessary for the growth of filterable virus. In certain instances cultures have been incubated with free access to oxygen. Li and Rivers 1 point out that a gradual simplification of the medium has taken place recently.2, 3, 4 They also emphasize the advantages of chick embryo tissue in saline over the more complex media employed earlier. Flexner and Noguchi 5 and Long, Olitsky and Rhodes 6 on the virus of poliomyelitis are typical of work done on cultures under oil. Dochez, Mills and Kneeland 7 and Powell and Clowes 8 used chick embryo tissue under vaseline seal.
In this type of culture apparently intact cells are seen after incubation. Muckenfuss and Rivers 9 and Muckenfuss 10 found that the addition of dead cells to the virus improved survival. Eagles and McClean 11 emphasized the unsatisfactory state of our knowledge regarding the role of tissue which had access to oxygen.
We attempted to define more accurately the condition of the cells supposed to be living in such preparations. Saline suspensions of chick embryo were studied since they are coming into general use.
Ten-day chick embryos were shaken with freshly broken pyrex glass in 10 cc. of Tyrode as described earlier. 12 Three cc. portions of the suspension were incubated in pyrex test tubes under sterile oil at 37.5° for the intervals stated. Control consisted of 2 cc. of the same suspension in a Carrel D5 flask. Immediately after preparation and at intervals of one hour 0.2 cc. portions were removed after mixing and planted in Carrel D3 flasks in 1 part heparinized rabbit plasma and 2 parts tissue extract, a medium well known to promote rapid growth.
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