The Growth and Morphology of Fibro-BlastsIn Vitroin Relation to Certain Properties of the Plasma Coagulum1

1. By placing blood plasma coagula containing growing cultures (fibroblasts from chick embryo) in a vertical position (vertical cultures) certain physical and quantitative chemical alterations of the medium occur under the influence of gravity; the effects of these upon the growth, morphology and products of differentiation (fibre formation) of the cultures are described. 2. In vertical cultures the normal circular shape of the cell colony remains undisturbed, indicating that neither gravity nor a gradient of metabolites seems to play a role controlling the direction of movement of fibroblastic cells. 3. Vertical cover-slip cultures show a greater radial extension (outgrowth) than the horizontal controls, apparently due to increased cell migration rather than to augmented cell division. 4. Vertical cultures of fibroblasts, both on cover-slips and in flasks, do not show the usual appearance of visible fat droplets. If fat appears at all in vertical cultures a fat-free sector can sometimes be observed in the lower half of the culture. Flattening of the coagulum retards but does not prevent the appearance of visible fat in normal cultures. 5. Under certain conditions the appearance of fat is an indicator of reduced activity since activity of fibroblastic cells (growth by migration) can be increased by preventing the accumulation of fat droplets in them. The latent period of offspring of a 10-day-old fat-free vertical culture is shortened as compared with that of offspring of the very fatty horizontal control of the same age. The greater activity observed in the vertical cover-slip cultures is apparently due to the non-appearance of fat. 6. Vertical cover-slip cultures after three days' cultivation show a slightly stronger formation of argyrophil fibres in the outer growth zone than the controls, but culture pairs fixed at a later time show no appreciable difference in fibre formation.