534 ROSS G. HARRISON 



EXPERIMENTS WITH CHICK TISSUES 



One hundred and two experiments divided into ten series 

 were made with chick tissue, comprising altogether 142 different 

 cultures since in some cases more than one culture was made 

 under the same cover. In three of the series the medium used 

 was Locke's solution, and in the other seven it was defibrinated 

 sermn. Clotted plasma was used for comparison in all series. 

 When plasma and serum were used the blood was always 

 taken from the same hen so as to have an identical fluid medimn 

 in all cases. 



Fixed support for the tissues was afforded by spider web 

 prepared as described above, by clotted plasma and by the lower 

 surface of the cover-slip. The latter was rendered available 

 by mounting the tissue in small drops. In other cases contact 

 was brought about after a tune by the spreading of the drop 

 which was originally large. This gives a firm attachment but 

 rarely a luxuriant growth because of the extreme thinness of the 

 fluid fihn.'-- Tissues from embryos varying in age from two to 

 nine days were used. The results are given briefly in table 3, 

 which shows the behavior of cells in the different media without, 

 however, attempting to analyze the behavior of different tissues. 

 Plasma preparations are 100 per cent positive. The cover- 

 slip preparations (i.e., those mounted in small drops) show also 

 a very high percentage of positive results while the spider web 

 cultures are less favorable, due probably as pointed out above, 

 to the extremely small amount of fluid used. The large drop 

 preparations are all negative except two which show some cell 

 wandering on the surface fihn. Several of the small drop cul- 

 tures also show slight cell movement on the surface. The fihn 

 cannot, however, be a very favorable surface for movement; 

 otherwise we should expect to find cells upon it much more fre- 



^2 Burrows (Trans. Am. Cong. Phys. and Surg., 1913) has shown that the amount 

 of cell migration depends upon the thickness of the layer of medium. There is 

 an optimum thickness above and below which less movement takes place; in the 

 thick layer because of insufficient oxygen and lesser concentration of repelling 

 waste products (acid), and in the very thin layer (below the optimum) because 

 of the small amount of nutrient medium. 



